UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-07139

Fidelity Hereford Street Trust

(Exact name of registrant as specified in charter)

245 Summer St., Boston, Massachusetts 02210

(Address of principal executive offices) (Zip code)

Cynthia Lo Bessette, Secretary

245 Summer St.

Boston, Massachusetts 02210

(Name and address of agent for service)

Registrant's telephone number, including area code:

617-563-7000


Date of fiscal year end:	April 30

Date of reporting period:	April 30, 2021

Item 1.

Reports to Stockholders

Fidelity® Treasury Only Money Market Fund

Annual Report

April 30, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Report of Independent Registered Public Accounting Firm
Trustees and Officers
Shareholder Expense Example
Distributions

To view a fund's proxy voting guidelines and proxy voting record for the 12-month period ended June 30, visit http://www.fidelity.com/proxyvotingresults or visit the Securities and Exchange Commission's (SEC) web site at http://www.sec.gov.

You may also call 1-800-544-8544 to request a free copy of the proxy voting guidelines.

Standard & Poor's, S&P and S&P 500 are registered service marks of The McGraw-Hill Companies, Inc. and have been licensed for use by Fidelity Distributors Corporation.

Other third-party marks appearing herein are the property of their respective owners.

This report and the financial statements contained herein are submitted for the general information of the shareholders of the Fund. This report is not authorized for distribution to prospective investors in the Fund unless preceded or accompanied by an effective prospectus.

A fund files its complete schedule of portfolio holdings with the SEC for the first and third quarters of each fiscal year on Form N-PORT. Forms N-PORT are available on the SEC’s web site at http://www.sec.gov. A fund's Forms N-PORT may be reviewed and copied at the SEC’s Public Reference Room in Washington, DC. Information regarding the operation of the SEC's Public Reference Room may be obtained by calling 1-800-SEC-0330.

For a complete list of a fund's portfolio holdings, view the most recent holdings listing, semiannual report, or annual report on Fidelity's web site at http://www.fidelity.com, http://www.institutional.fidelity.com, or http://www.401k.com, as applicable.

NOT FDIC INSURED •MAY LOSE VALUE •NO BANK GUARANTEE

Neither the Fund nor Fidelity Distributors Corporation is a bank.

Note to Shareholders:

Early in 2020, the outbreak and spread of a new coronavirus emerged as a public health emergency that had a major influence on financial markets, primarily based on its impact on the global economy and the outlook for corporate earnings. The virus causes a respiratory disease known as COVID-19. On March 11, 2020 the World Health Organization declared the COVID-19 outbreak a pandemic, citing sustained risk of further global spread.

In the weeks following, as the crisis worsened, we witnessed an escalating human tragedy with wide-scale social and economic consequences from coronavirus-containment measures. The outbreak of COVID-19 prompted a number of measures to limit the spread, including travel and border restrictions, quarantines, and restrictions on large gatherings. In turn, these resulted in lower consumer activity, diminished demand for a wide range of products and services, disruption in manufacturing and supply chains, and – given the wide variability in outcomes regarding the outbreak – significant market uncertainty and volatility. Amid the turmoil, global governments and central banks took unprecedented action to help support consumers, businesses, and the broader economies, and to limit disruption to financial systems.

The situation continues to unfold, and the extent and duration of its impact on financial markets and the economy remain highly uncertain. Extreme events such as the coronavirus crisis are “exogenous shocks” that can have significant adverse effects on mutual funds and their investments. Although multiple asset classes may be affected by market disruption, the duration and impact may not be the same for all types of assets.

Fidelity is committed to helping you stay informed amid news about COVID-19 and during increased market volatility, and we’re taking extra steps to be responsive to customer needs. We encourage you to visit our websites, where we offer ongoing updates, commentary, and analysis on the markets and our funds.

Investment Summary/Performance (Unaudited)

Effective Maturity Diversification as of April 30, 2021

Days	% of fund's investments 4/30/21
1 - 7	25.9
8 - 30	34.4
31 - 60	18.9
61 - 90	12.0
91 - 180	8.5
>180	0.3

Effective maturity is determined in accordance with the requirements of Rule 2a-7 under the Investment Company Act of 1940.

Asset Allocation (% of fund's net assets)

As of April 30, 2021
	U.S. Treasury Debt	107.3%
	Net Other Assets (Liabilities)^*	(7.3)%

* Net Other Assets (Liabilities) are not included in the pie chart

Current 7-Day Yields

	4/30/21
Fidelity® Treasury Only Money Market Fund	0.01%

Yield refers to the income paid by the Fund over a given period. Yield for money market funds is usually for seven-day periods, as it is here, though it is expressed as an annual percentage rate. Past performance is no guarantee of future results. Yield will vary and it's possible to lose money investing in the Fund. A portion of the Fund's expenses was reimbursed and/or waived. Absent such reimbursements and/or waivers the yield for the period ending April 30, 2021, the most recent period shown in the table, would have been (.35)%.

Schedule of Investments April 30, 2021

Showing Percentage of Net Assets

U.S. Treasury Debt - 107.3%
	Yield(a)	Principal Amount (000s)	Value (000s)
U.S. Treasury Obligations - 107.3%
U.S. Treasury Bills
5/4/21 to 10/28/21	0.01 to 0.11%	$3,248,730	$3,248,554
U.S. Treasury Bonds
5/15/21	0.10	7,000	7,022
U.S. Treasury Notes
5/15/21 to 4/30/23	0.01 to 0.32 (b)	826,908	827,081
TOTAL U.S. TREASURY DEBT
(Cost $4,082,657)			4,082,657
TOTAL INVESTMENT IN SECURITIES - 107.3%
(Cost $4,082,657)			4,082,657
NET OTHER ASSETS (LIABILITIES) - (7.3)%			(278,361)
NET ASSETS - 100%			$3,804,296

The date shown for securities represents the date when principal payments must be paid, taking into account any call options exercised by the issuer and any permissible maturity shortening features other than interest rate resets.

Legend

(a) Yield represents either the annualized yield at the date of purchase, or the stated coupon rate, or, for floating and adjustable rate securities, the rate at period end.

(b) Coupon rates for floating and adjustable rate securities reflect the rates in effect at period end.

Investment Valuation

All investments are categorized as Level 2 under the Fair Value Hierarchy. The inputs or methodology used for valuing securities may not be an indication of the risk associated with investing in those securities. For more information on valuation inputs please refer to the Investment Valuation section in the accompanying Notes to Financial Statements.

See accompanying notes which are an integral part of the financial statements.

Financial Statements

Statement of Assets and Liabilities

Amounts in thousands (except per-share amount)		April 30, 2021
Assets
Investment in securities, at value — See accompanying schedule: Unaffiliated issuers (cost $4,082,657)		$4,082,657
Receivable for fund shares sold		5,169
Interest receivable		1,116
Total assets		4,088,942
Liabilities
Payable to custodian bank	$1
Payable for investments purchased	$270,005
Payable for fund shares redeemed	14,435
Distributions payable	3
Accrued management fee	202
Total liabilities		284,646
Net Assets		$3,804,296
Net Assets consist of:
Paid in capital		$3,804,232
Total accumulated earnings (loss)		64
Net Assets		$3,804,296
Net Asset Value, offering price and redemption price per share ($3,804,296 ÷ 3,803,419 shares)		$1.00

See accompanying notes which are an integral part of the financial statements.

Statement of Operations

Amounts in thousands		Year ended April 30, 2021
Investment Income
Interest		$6,951
Expenses
Management fee	$18,209
Independent trustees' fees and expenses	14
Total expenses before reductions	18,223
Expense reductions	(11,706)
Total expenses after reductions		6,517
Net investment income (loss)		434
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		4
Total net realized gain (loss)		4
Net increase in net assets resulting from operations		$438

See accompanying notes which are an integral part of the financial statements.

Statement of Changes in Net Assets

Amounts in thousands	Year ended April 30, 2021	Year ended April 30, 2020
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$434	$40,343
Net realized gain (loss)	4	5
Net increase in net assets resulting from operations	438	40,348
Distributions to shareholders	(434)	(40,347)
Share transactions
Proceeds from sales of shares	1,481,386	4,322,438
Reinvestment of distributions	394	37,205
Cost of shares redeemed	(2,722,827)	(2,137,693)
Net increase (decrease) in net assets and shares resulting from share transactions	(1,241,047)	2,221,950
Total increase (decrease) in net assets	(1,241,043)	2,221,951
Net Assets
Beginning of period	5,045,339	2,823,388
End of period	$3,804,296	$5,045,339
Other Information
Shares
Sold	1,481,386	4,322,438
Issued in reinvestment of distributions	394	37,205
Redeemed	(2,722,827)	(2,137,693)
Net increase (decrease)	(1,241,047)	2,221,950

See accompanying notes which are an integral part of the financial statements.

Financial Highlights

Fidelity Treasury Only Money Market Fund


Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.014	.018	.008	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.014	.018	.008	–^A
Distributions from net investment income	–^A	(.014)	(.018)	(.008)	–^A
Total distributions	–^A	(.014)	(.018)	(.008)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.01%	1.39%	1.79%	.77%	.07%
Ratios to Average Net Assets^C,^D
Expenses before reductions	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.15%	.42%	.42%	.42%	.38%
Expenses net of all reductions	.15%	.42%	.42%	.42%	.38%
Net investment income (loss)	.01%	1.27%	1.76%	.76%	.06%
Supplemental Data
Net assets, end of period (in millions)	$3,804	$5,045	$2,823	$3,173	$3,720

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^C Fees and expenses of any underlying mutual funds or exchange-traded funds (ETFs) are not included in the Fund's expense ratio. The Fund indirectly bears its proportionate share of these expenses.

^D Expense ratios reflect operating expenses of the class. Expenses before reductions do not reflect amounts reimbursed, waived, or reduced through arrangements with the investment advisor, brokerage services, or other offset arrangements, if applicable, and do not represent the amount paid by the class during periods when reimbursements, waivers or reductions occur.

See accompanying notes which are an integral part of the financial statements.

Notes to Financial Statements

For the period ended April 30, 2021
(Amounts in thousands except percentages)

1. Organization.

Fidelity Treasury Only Money Market Fund (the Fund) is a fund of Fidelity Hereford Street Trust (the Trust) and is authorized to issue an unlimited number of shares. Share transactions on the Statement of Changes in Net Assets may contain exchanges between affiliated funds. The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Delaware statutory trust.

2. Significant Accounting Policies.

The Fund is an investment company and applies the accounting and reporting guidance of the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946 Financial Services - Investment Companies. The financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP), which require management to make certain estimates and assumptions at the date of the financial statements. Actual results could differ from those estimates. Subsequent events, if any, through the date that the financial statements were issued have been evaluated in the preparation of the financial statements. The Fund's Schedule of Investments lists any underlying mutual funds or exchange-traded funds (ETFs) but does not include the underlying holdings of these funds. The following summarizes the significant accounting policies of the Fund:

Investment Valuation. The Fund categorizes the inputs to valuation techniques used to value its investments into a disclosure hierarchy consisting of three levels as shown below:

Level 1 – quoted prices in active markets for identical investments
Level 2 – other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, etc.)
Level 3 – unobservable inputs (including the Fund's own assumptions based on the best information available)

As permitted by compliance with certain conditions under Rule 2a-7 of the 1940 Act, securities are valued at amortized cost, which approximates fair value. The amortized cost of an instrument is determined by valuing it at its original cost and thereafter amortizing any discount or premium from its face value at a constant rate until maturity. Securities held by a money market fund are generally high quality and liquid; however, they are reflected as Level 2 because the inputs used to determine fair value are not quoted prices in an active market.

Expenses. Expenses directly attributable to a fund are charged to that fund. Expenses attributable to more than one fund are allocated among the respective funds on the basis of relative net assets or other appropriate methods. Expenses included in the accompanying financial statements reflect the expenses of that fund and do not include any expenses associated with any underlying mutual funds or exchange-traded funds. Although not included in a fund's expenses, a fund indirectly bears its proportionate share of these expenses through the net asset value of each underlying mutual fund or exchange-traded fund. Expense estimates are accrued in the period to which they relate and adjustments are made when actual amounts are known.

Income Tax Information and Distributions to Shareholders. Each year, the Fund intends to qualify as a regulated investment company under Subchapter M of the Internal Revenue Code, including distributing substantially all of its taxable income and realized gains. As a result, no provision for U.S. Federal income taxes is required. As of April 30, 2021, the Fund did not have any unrecognized tax benefits in the financial statements; nor is the Fund aware of any tax positions for which it is reasonably possible that the total amounts of unrecognized tax benefits will significantly change in the next twelve months. The Fund files a U.S. federal tax return, in addition to state and local tax returns as required. The Fund's federal income tax returns are subject to examination by the Internal Revenue Service (IRS) for a period of three fiscal years after they are filed. State and local tax returns may be subject to examination for an additional fiscal year depending on the jurisdiction.

Distributions are declared and recorded daily and paid monthly from net investment income. Distributions from realized gains, if any, are declared and recorded on the ex-dividend date. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from GAAP. In addition, the Fund claimed a portion of the payment made to redeeming shareholders as a distribution for income tax purposes.

Capital accounts within the financial statements are adjusted for permanent book-tax differences. These adjustments have no impact on net assets or the results of operations. Capital accounts are not adjusted for temporary book-tax differences which will reverse in a subsequent period.

Book-tax differences are primarily due to losses deferred due to wash sales.

As of period end, the cost and unrealized appreciation (depreciation) in securities for federal income tax purposes were as follows:

Gross unrealized appreciation	$–
Gross unrealized depreciation	–
Net unrealized appreciation (depreciation)	$–
Tax Cost	$4,082,657

The tax-based components of distributable earnings as of period end were as follows:

Undistributed ordinary income

$72

The tax character of distributions paid was as follows:

	April 30, 2021	April 30, 2020
Ordinary Income	$434	$ 40,347

3. Fees and Other Transactions with Affiliates.

Management Fee. Fidelity Management & Research Company LLC (the investment adviser) and its affiliates provide the Fund with investment management related services for which the Fund pays a monthly management fee that is based on an annual rate of .42% of the Fund's average net assets. Under the management contract, the investment adviser pays all other expenses, except the compensation of the independent Trustees and certain other expenses such as interest expense. The management fee is reduced by an amount equal to the fees and expenses paid by the Fund to the independent Trustees.

Interfund Trades. Funds may purchase from or sell securities to other Fidelity Funds under procedures adopted by the Board. The procedures have been designed to ensure these interfund trades are executed in accordance with Rule 17a-7 of the 1940 Act.

4. Expense Reductions.

The investment adviser or its affiliates voluntarily agreed to waive certain fees in order to avoid a negative yield. Such arrangements may be discontinued by the investment adviser at any time. For the period, the amount of the waiver was $11,671.

In addition, through arrangements with the Fund's custodian, credits realized as a result of certain uninvested cash balances were used to reduce the Fund's expenses by $35.

5. Other.

Fund's organizational documents provide former and current trustees and officers with a limited indemnification against liabilities arising in connection with the performance of their duties to the fund. In the normal course of business, the fund may also enter into contracts that provide general indemnifications. The fund's maximum exposure under these arrangements is unknown as this would be dependent on future claims that may be made against the fund. The risk of material loss from such claims is considered remote.

6. Coronavirus (COVID-19) Pandemic.

An outbreak of COVID-19 first detected in China during December 2019 has since spread globally and was declared a pandemic by the World Health Organization during March 2020. Developments that disrupt global economies and financial markets, such as the COVID-19 pandemic, may magnify factors that affect the Fund's performance.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Fidelity Hereford Street Trust and Shareholders of Fidelity Treasury Only Money Market Fund

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities, including the schedule of investments, of Fidelity Treasury Only Money Market Fund (one of the funds constituting Fidelity Hereford Street Trust, referred to hereafter as the “Fund”) as of April 30, 2021, the related statement of operations for the year ended April 30, 2021, the statement of changes in net assets for each of the two years in the period ended April 30, 2021, including the related notes, and the financial highlights for each of the five years in the period ended April 30, 2021 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period ended April 30, 2021 and the financial highlights for each of the five years in the period ended April 30, 2021 in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Fund’s management. Our responsibility is to express an opinion on the Fund’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits of these financial statements in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of April 30, 2021 by correspondence with the custodian and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

June 14, 2021

We have served as the auditor of one or more investment companies in the Fidelity group of funds since 1932.

Trustees and Officers

The Trustees, Members of the Advisory Board (if any), and officers of the trust and fund, as applicable, are listed below. The Board of Trustees governs the fund and is responsible for protecting the interests of shareholders. The Trustees are experienced executives who meet periodically throughout the year to oversee the fund's activities, review contractual arrangements with companies that provide services to the fund, oversee management of the risks associated with such activities and contractual arrangements, and review the fund's performance. Each of the Trustees oversees 283 funds.

The Trustees hold office without limit in time except that (a) any Trustee may resign; (b) any Trustee may be removed by written instrument, signed by at least two-thirds of the number of Trustees prior to such removal; (c) any Trustee who requests to be retired or who has become incapacitated by illness or injury may be retired by written instrument signed by a majority of the other Trustees; and (d) any Trustee may be removed at any special meeting of shareholders by a two-thirds vote of the outstanding voting securities of the trust. Each Trustee who is not an interested person (as defined in the 1940 Act) of the trust and the fund is referred to herein as an Independent Trustee. Each Independent Trustee shall retire not later than the last day of the calendar year in which his or her 75th birthday occurs. The Independent Trustees may waive this mandatory retirement age policy with respect to individual Trustees. Officers and Advisory Board Members hold office without limit in time, except that any officer or Advisory Board Member may resign or may be removed by a vote of a majority of the Trustees at any regular meeting or any special meeting of the Trustees. Except as indicated, each individual has held the office shown or other offices in the same company for the past five years.

The fund’s Statement of Additional Information (SAI) includes more information about the Trustees. To request a free copy, call Fidelity at 1-800-544-8544.

Experience, Skills, Attributes, and Qualifications of the Trustees. The Governance and Nominating Committee has adopted a statement of policy that describes the experience, qualifications, attributes, and skills that are necessary and desirable for potential Independent Trustee candidates (Statement of Policy). The Board believes that each Trustee satisfied at the time he or she was initially elected or appointed a Trustee, and continues to satisfy, the standards contemplated by the Statement of Policy. The Governance and Nominating Committee also engages professional search firms to help identify potential Independent Trustee candidates who have the experience, qualifications, attributes, and skills consistent with the Statement of Policy. From time to time, additional criteria based on the composition and skills of the current Independent Trustees, as well as experience or skills that may be appropriate in light of future changes to board composition, business conditions, and regulatory or other developments, have also been considered by the professional search firms and the Governance and Nominating Committee. In addition, the Board takes into account the Trustees' commitment and participation in Board and committee meetings, as well as their leadership of standing and ad hoc committees throughout their tenure.

In determining that a particular Trustee was and continues to be qualified to serve as a Trustee, the Board has considered a variety of criteria, none of which, in isolation, was controlling. The Board believes that, collectively, the Trustees have balanced and diverse experience, qualifications, attributes, and skills, which allow the Board to operate effectively in governing the fund and protecting the interests of shareholders. Information about the specific experience, skills, attributes, and qualifications of each Trustee, which in each case led to the Board's conclusion that the Trustee should serve (or continue to serve) as a trustee of the fund, is provided below.

Board Structure and Oversight Function. Abigail P. Johnson is an interested person and currently serves as Chairman. The Trustees have determined that an interested Chairman is appropriate and benefits shareholders because an interested Chairman has a personal and professional stake in the quality and continuity of services provided to the fund. Independent Trustees exercise their informed business judgment to appoint an individual of their choosing to serve as Chairman, regardless of whether the Trustee happens to be independent or a member of management. The Independent Trustees have determined that they can act independently and effectively without having an Independent Trustee serve as Chairman and that a key structural component for assuring that they are in a position to do so is for the Independent Trustees to constitute a substantial majority for the Board. The Independent Trustees also regularly meet in executive session. Arthur E. Johnson serves as Chairman of the Independent Trustees and as such (i) acts as a liaison between the Independent Trustees and management with respect to matters important to the Independent Trustees and (ii) with management prepares agendas for Board meetings.

Fidelity^® funds are overseen by different Boards of Trustees. The fund's Board oversees Fidelity's investment-grade bond, money market, asset allocation and certain equity funds, and other Boards oversee Fidelity's high income and other equity funds. The asset allocation funds may invest in Fidelity^® funds that are overseen by such other Boards. The use of separate Boards, each with its own committee structure, allows the Trustees of each group of Fidelity^® funds to focus on the unique issues of the funds they oversee, including common research, investment, and operational issues. On occasion, the separate Boards establish joint committees to address issues of overlapping consequences for the Fidelity^® funds overseen by each Board.

The Trustees operate using a system of committees to facilitate the timely and efficient consideration of all matters of importance to the Trustees, the fund, and fund shareholders and to facilitate compliance with legal and regulatory requirements and oversight of the fund's activities and associated risks. The Board, acting through its committees, has charged FMR and its affiliates with (i) identifying events or circumstances the occurrence of which could have demonstrably adverse effects on the fund's business and/or reputation; (ii) implementing processes and controls to lessen the possibility that such events or circumstances occur or to mitigate the effects of such events or circumstances if they do occur; and (iii) creating and maintaining a system designed to evaluate continuously business and market conditions in order to facilitate the identification and implementation processes described in (i) and (ii) above. Because the day-to-day operations and activities of the fund are carried out by or through FMR, its affiliates, and other service providers, the fund's exposure to risks is mitigated but not eliminated by the processes overseen by the Trustees. While each of the Board's committees has responsibility for overseeing different aspects of the fund's activities, oversight is exercised primarily through the Operations and Audit Committees. In addition, an ad hoc Board committee of Independent Trustees has worked with FMR to enhance the Board's oversight of investment and financial risks, legal and regulatory risks, technology risks, and operational risks, including the development of additional risk reporting to the Board. The Operations Committee also worked and continues to work with FMR to enhance the stress tests required under SEC regulations for money market funds. Appropriate personnel, including but not limited to the fund's Chief Compliance Officer (CCO), FMR's internal auditor, the independent accountants, the fund's Treasurer and portfolio management personnel, make periodic reports to the Board's committees, as appropriate, including an annual review of Fidelity's risk management program for the Fidelity^® funds. The responsibilities of each standing committee, including their oversight responsibilities, are described further under "Standing Committees of the Trustees."

Interested Trustees*:

Correspondence intended for a Trustee who is an interested person may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Abigail P. Johnson (1961)

Year of Election or Appointment: 2009

Trustee

Chairman of the Board of Trustees

Ms. Johnson also serves as Trustee of other Fidelity^® funds. Ms. Johnson serves as Chairman (2016-present), Chief Executive Officer (2014-present), and Director (2007-present) of FMR LLC (diversified financial services company), President of Fidelity Financial Services (2012-present) and President of Personal, Workplace and Institutional Services (2005-present). Ms. Johnson is Chairman and Director of Fidelity Management & Research Company LLC (investment adviser firm, 2011-present). Previously, Ms. Johnson served as Chairman and Director of FMR Co., Inc. (investment adviser firm, 2011-2019), Vice Chairman (2007-2016) and President (2013-2016) of FMR LLC, President and a Director of Fidelity Management & Research Company (2001-2005), a Trustee of other investment companies advised by Fidelity Management & Research Company, Fidelity Investments Money Management, Inc. (investment adviser firm), and FMR Co., Inc. (2001-2005), Senior Vice President of the Fidelity^® funds (2001-2005), and managed a number of Fidelity^® funds. Ms. Abigail P. Johnson and Mr. Arthur E. Johnson are not related.

Jennifer Toolin McAuliffe (1959)

Year of Election or Appointment: 2016

Trustee

Ms. McAuliffe also serves as Trustee of other Fidelity^® funds and as Trustee of Fidelity Charitable (2020-present). Previously, Ms. McAuliffe served as Co-Head of Fixed Income of Fidelity Investments Limited (now known as FIL Limited (FIL)) (diversified financial services company), Director of Research for FIL’s credit and quantitative teams in London, Hong Kong and Tokyo and Director of Research for taxable and municipal bonds at Fidelity Investments Money Management, Inc. Ms. McAuliffe previously served as a member of the Advisory Board of certain Fidelity^® funds (2016). Ms. McAuliffe was previously a lawyer at Ropes & Gray LLP and currently serves as director or trustee of several not-for-profit entities.

* Determined to be an “Interested Trustee” by virtue of, among other things, his or her affiliation with the trust or various entities under common control with FMR.

+ The information includes the Trustee's principal occupation during the last five years and other information relating to the experience, attributes, and skills relevant to the Trustee's qualifications to serve as a Trustee, which led to the conclusion that the Trustee should serve as a Trustee for the fund.

Independent Trustees:

Correspondence intended for an Independent Trustee may be sent to Fidelity Investments, P.O. Box 55235, Boston, Massachusetts 02205-5235.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Elizabeth S. Acton (1951)

Year of Election or Appointment: 2013

Trustee

Ms. Acton also serves as Trustee of other Fidelity^® funds. Prior to her retirement, Ms. Acton served as Executive Vice President, Finance (2011-2012), Executive Vice President, Chief Financial Officer (2002-2011) and Treasurer (2004-2005) of Comerica Incorporated (financial services). Prior to joining Comerica, Ms. Acton held a variety of positions at Ford Motor Company (1983-2002), including Vice President and Treasurer (2000-2002) and Executive Vice President and Chief Financial Officer of Ford Motor Credit Company (1998-2000). Ms. Acton currently serves as a member of the Board and Audit and Finance Committees of Beazer Homes USA, Inc. (homebuilding, 2012-present). Ms. Acton previously served as a member of the Advisory Board of certain Fidelity^® funds (2013-2016).

Ann E. Dunwoody (1953)

Year of Election or Appointment: 2018

Trustee

General Dunwoody also serves as Trustee of other Fidelity^® funds. General Dunwoody (United States Army, Retired) was the first woman in U.S. military history to achieve the rank of four-star general and prior to her retirement in 2012 held a variety of positions within the U.S. Army, including Commanding General, U.S. Army Material Command (2008-2012). General Dunwoody currently serves as President of First to Four LLC (leadership and mentoring services, 2012-present), a member of the Board and Nomination and Corporate Governance Committees of Kforce Inc. (professional staffing services, 2016-present) and a member of the Board of Automattic Inc. (software engineering, 2018-present). Previously, General Dunwoody served as a member of the Advisory Board and Nominating and Corporate Governance Committee of L3 Technologies, Inc. (communication, electronic, sensor and aerospace systems, 2013-2019) and a member of the Board and Audit and Sustainability and Corporate Responsibility Committees of Republic Services, Inc. (waste collection, disposal and recycling, 2013-2016). Ms. Dunwoody also serves on several boards for non-profit organizations, including as a member of the Board, Chair of the Nomination and Governance Committee and a member of the Audit Committee of Logistics Management Institute (consulting non-profit, 2012-present), a member of the Council of Trustees for the Association of the United States Army (advocacy non-profit, 2013-present), a member of the Board of Florida Institute of Technology (2015-present) and a member of the Board of ThanksUSA (military family education non-profit, 2014-present). General Dunwoody previously served as a member of the Advisory Board of certain Fidelity^® funds (2018).

John Engler (1948)

Year of Election or Appointment: 2014

Trustee

Mr. Engler also serves as Trustee of other Fidelity^® funds. Previously, Mr. Engler served as Governor of Michigan (1991-2003), President of the Business Roundtable (2011-2017) and interim President of Michigan State University (2018-2019). Mr. Engler currently serves as a member of the Board of Stride, Inc. (formerly K12 Inc.) (technology-based education company, 2012-present). Previously, Mr. Engler served as a member of the Board of Universal Forest Products (manufacturer and distributor of wood and wood-alternative products, 2003-2019) and Trustee of The Munder Funds (2003-2014). Mr. Engler previously served as a member of the Advisory Board of certain Fidelity^® funds (2014-2016).

Robert F. Gartland (1951)

Year of Election or Appointment: 2010

Trustee

Mr. Gartland also serves as Trustee of other Fidelity^® funds. Prior to his retirement, Mr. Gartland held a variety of positions at Morgan Stanley (financial services, 1979-2007), including Managing Director (1987-2007) and Chase Manhattan Bank (1975-1978). Mr. Gartland previously served as Chairman and an investor in Gartland & Mellina Group Corp. (consulting, 2009-2019), as a member of the Board of National Securities Clearing Corporation (1993-1996) and as Chairman of TradeWeb (2003-2004).

Arthur E. Johnson (1947)

Year of Election or Appointment: 2008

Trustee

Chairman of the Independent Trustees

Mr. Johnson also serves as Trustee of other Fidelity^® funds. Prior to his retirement, Mr. Johnson served as Senior Vice President of Corporate Strategic Development of Lockheed Martin Corporation (defense contractor, 1999-2009). Mr. Johnson currently serves as a member of the Board of Booz Allen Hamilton (management consulting, 2011-present). Mr. Johnson previously served as a member of the Board of Eaton Corporation plc (diversified power management, 2009-2019) and a member of the Board of AGL Resources, Inc. (holding company, 2002-2016). Mr. Johnson previously served as Vice Chairman (2015-2018) of the Independent Trustees of certain Fidelity^® funds. Mr. Arthur E. Johnson is not related to Ms. Abigail P. Johnson.

Michael E. Kenneally (1954)

Year of Election or Appointment: 2009

Trustee

Vice Chairman of the Independent Trustees

Mr. Kenneally also serves as Trustee of other Fidelity^® funds. Prior to his retirement, Mr. Kenneally served as Chairman and Global Chief Executive Officer of Credit Suisse Asset Management and as Executive Vice President and Chief Investment Officer for Bank of America Corporation, where he was responsible for the bank’s money-management products. Previously at Bank of America, Mr. Kenneally managed the principal investment research functions and also spent more than a decade as portfolio manager for various equity and fixed-income funds and institutional accounts. He began his career as a research analyst in 1983 and was awarded the Chartered Financial Analyst (CFA) designation in 1991.

Marie L. Knowles (1946)

Year of Election or Appointment: 2001

Trustee

Ms. Knowles also serves as Trustee of other Fidelity^® funds. Prior to her retirement, Ms. Knowles held several positions at Atlantic Richfield Company (diversified energy), including Executive Vice President and Chief Financial Officer (1996-2000), Senior Vice President (1993-1996) and President of ARCO Transportation Company (pipeline and tanker operations, 1993-1996). Ms. Knowles currently serves as a member of the Board of McKesson Corporation (healthcare service, since 2002), a member of the Board of the Santa Catalina Island Company (real estate, 2009-present), a member of the Investment Company Institute Board of Governors and a member of the Governing Council of the Independent Directors Council (2014-present). Ms. Knowles also serves as a member of the Advisory Board for the School of Engineering of the University of Southern California. Ms. Knowles previously served as Chairman (2015-2018) and Vice Chairman (2012-2015) of the Independent Trustees of certain Fidelity^® funds.

Mark A. Murray (1954)

Year of Election or Appointment: 2016

Trustee

Mr. Murray also serves as Trustee of other Fidelity^® funds. Previously, Mr. Murray served as Co-Chief Executive Officer (2013-2016), President (2006-2013) and Vice Chairman (2013-2020) of Meijer, Inc. Mr. Murray serves as a member of the Board (2009-present) and Public Policy and Responsibility Committee (2009-present) and Chair of the Nuclear Review Committee (2019-present) of DTE Energy Company (diversified energy company). Mr. Murray previously served as a member of the Board of Spectrum Health (not-for-profit health system, 2015-2019) and as a member of the Board and Audit Committee and Chairman of the Nominating and Corporate Governance Committee of Universal Forest Products, Inc. (manufacturer and distributor of wood and wood-alternative products, 2004-2016). Mr. Murray also serves as a member of the Board of many community and professional organizations. Mr. Murray previously served as a member of the Advisory Board of certain Fidelity^® funds (2016).

Advisory Board Members and Officers:

Correspondence intended for an officer may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210. Officers appear below in alphabetical order.

Name, Year of Birth; Principal Occupation

Robert W. Helm (1957)

Year of Election or Appointment: 2021

Member of the Advisory Board

Mr. Helm also serves as a Member of the Advisory Board of other Fidelity® funds. Mr. Helm was formerly Deputy Chairman (2003-2020), partner (1991-2020) and an associate (1984-1991) of Dechert LLP (formerly Dechert Price & Rhoads). Mr. Helm currently serves on boards and committees of several not-for-profit organizations.

Craig S. Brown (1977)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Brown also serves as Assistant Treasurer of other funds. Mr. Brown is an employee of Fidelity Investments (2013-present).

John J. Burke III (1964)

Year of Election or Appointment: 2018

Chief Financial Officer

Mr. Burke also serves as Chief Financial Officer of other funds. Mr. Burke serves as Head of Investment Operations for Fidelity Fund and Investment Operations (2018-present) and is an employee of Fidelity Investments (1998-present). Previously Mr. Burke served as head of Asset Management Investment Operations (2012-2018).

David J. Carter (1973)

Year of Election or Appointment: 2020

Assistant Secretary

Mr. Carter also serves as Assistant Secretary of other funds. Mr. Carter serves as Vice President, Associate General Counsel (2010-present) and is an employee of Fidelity Investments (2005-present).

Jonathan Davis (1968)

Year of Election or Appointment: 2010

Assistant Treasurer

Mr. Davis also serves as Assistant Treasurer of other funds. Mr. Davis serves as Assistant Treasurer of FMR Capital, Inc. (2017-present) and is an employee of Fidelity Investments. Previously, Mr. Davis served as Vice President and Associate General Counsel of FMR LLC (diversified financial services company, 2003-2010).

Laura M. Del Prato (1964)

Year of Election or Appointment: 2018

President and Treasurer

Ms. Del Prato also serves as an officer of other funds. Ms. Del Prato is an employee of Fidelity Investments (2017-present). Previously, Ms. Del Prato served as President and Treasurer of The North Carolina Capital Management Trust: Cash Portfolio and Term Portfolio (2018-2020). Prior to joining Fidelity Investments, Ms. Del Prato served as a Managing Director and Treasurer of the JPMorgan Mutual Funds (2014-2017). Prior to JPMorgan, Ms. Del Prato served as a partner at Cohen Fund Audit Services (accounting firm, 2012-2013) and KPMG LLP (accounting firm, 2004-2012).

Colm A. Hogan (1973)

Year of Election or Appointment: 2016

Assistant Treasurer

Mr. Hogan also serves as an officer of other funds. Mr. Hogan serves as Assistant Treasurer of FMR Capital, Inc. (2017-present) and is an employee of Fidelity Investments (2005-present). Previously, Mr. Hogan served as Deputy Treasurer of certain Fidelity^® funds (2016-2020) and Assistant Treasurer of certain Fidelity^® funds (2016-2018).

Cynthia Lo Bessette (1969)

Year of Election or Appointment: 2019

Secretary and Chief Legal Officer (CLO)

Ms. Lo Bessette also serves as an officer of other funds. Ms. Lo Bessette serves as CLO, Secretary, and Senior Vice President of Fidelity Management & Research Company LLC (investment adviser firm, 2019-present); and CLO of Fidelity Management & Research (Hong Kong) Limited, FMR Investment Management (UK) Limited, and Fidelity Management & Research (Japan) Limited (investment adviser firms, 2019-present). She is a Senior Vice President and Deputy General Counsel of FMR LLC (diversified financial services company, 2019-present), and is an employee of Fidelity Investments. Previously, Ms. Lo Bessette served as CLO, Secretary, and Senior Vice President of FMR Co., Inc. (investment adviser firm, 2019); Secretary of Fidelity SelectCo, LLC and Fidelity Investments Money Management, Inc. (investment adviser firms, 2019). Prior to joining Fidelity Investments, Ms. Lo Bessette was Executive Vice President, General Counsel (2016-2019) and Senior Vice President, Deputy General Counsel (2015-2016) of OppenheimerFunds (investment management company) and Deputy Chief Legal Officer (2013-2015) of Jennison Associates LLC (investment adviser firm).

Chris Maher (1972)

Year of Election or Appointment: 2013

Assistant Treasurer

Mr. Maher also serves as an officer of other funds. Mr. Maher serves as Assistant Treasurer of FMR Capital, Inc. (2017-present), and is an employee of Fidelity Investments (2008-present). Previously, Mr. Maher served as Assistant Treasurer of certain funds (2013-2020); Vice President of Asset Management Compliance (2013), Vice President of the Program Management Group of FMR (investment adviser firm, 2010-2013), and Vice President of Valuation Oversight (2008-2010).

Jamie Pagliocco (1964)

Year of Election or Appointment: 2020

Vice President

Mr. Pagliocco also serves as Vice President of other funds. Mr. Pagliocco serves as President of Fixed Income (2020-present), and is an employee of Fidelity Investments (2001-present). Previously, Mr. Pagliocco served as Co-Chief Investment Officer – Bond (2017-2020), Global Head of Bond Trading (2016-2019), and as a portfolio manager.

Kenneth B. Robins (1969)

Year of Election or Appointment: 2020

Chief Compliance Officer

Mr. Robins also serves as an officer of other funds. Mr. Robins serves as Compliance Officer of Fidelity Management & Research Company LLC (investment adviser firm, 2016-present) and is an employee of Fidelity Investments (2004-present). Previously, Mr. Robins served as Compliance Officer of FMR Co., Inc. (investment adviser firm, 2016-2019), as Executive Vice President of Fidelity Investments Money Management, Inc. (investment adviser firm, 2013-2016) and served in other fund officer roles.

Brett Segaloff (1972)

Year of Election or Appointment: 2021

Anti-Money Laundering (AML) Officer

Mr. Segaloff also serves as an AML Officer of other funds and other related entities. He is Director, Anti-Money Laundering (2007-present) of FMR LLC (diversified financial services company) and is an employee of Fidelity Investments (1996-present).

Stacie M. Smith (1974)

Year of Election or Appointment: 2013

Assistant Treasurer

Ms. Smith also serves as an officer of other funds. Ms. Smith serves as Assistant Treasurer of FMR Capital, Inc. (2017-present), is an employee of Fidelity Investments (2009-present), and has served in other fund officer roles. Prior to joining Fidelity Investments, Ms. Smith served as Senior Audit Manager of Ernst & Young LLP (accounting firm, 1996-2009). Previously, Ms. Smith served as Assistant Treasurer (2013-2019) and Deputy Treasurer (2013-2016) of certain Fidelity^® funds.

Marc L. Spector (1972)

Year of Election or Appointment: 2016

Deputy Treasurer

Mr. Spector also serves as an officer of other funds. Mr. Spector serves as Assistant Treasurer of FMR Capital, Inc. (2017-present) and is an employee of Fidelity Investments (2016-present). Prior to joining Fidelity Investments, Mr. Spector served as Director at the Siegfried Group (accounting firm, 2013-2016), and prior to Siegfried Group as audit senior manager at Deloitte & Touche LLP (accounting firm, 2005-2013).

Jim Wegmann (1979)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Wegmann also serves as Assistant Treasurer of other funds. Mr. Wegmann is an employee of Fidelity Investments (2011-present).

Shareholder Expense Example

As a shareholder, you incur two types of costs: (1) transaction costs, which may include sales charges (loads) on purchase payments or redemption proceeds, as applicable and (2) ongoing costs, which generally include management fees, distribution and/or service (12b-1) fees and other Fund expenses. This Example is intended to help you understand your ongoing costs (in dollars) of investing in a fund and to compare these costs with the ongoing costs of investing in other mutual funds.

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (November 1, 2020 to April 30, 2021).

Actual Expenses

The first line of the accompanying table provides information about actual account values and actual expenses. You may use the information in this line, together with the amount you invested, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000.00 (for example, an $8,600 account value divided by $1,000.00 = 8.6), then multiply the result by the number in the first line for a class/Fund under the heading entitled "Expenses Paid During Period" to estimate the expenses you paid on your account during this period. If any fund is a shareholder of any underlying mutual funds or exchange-traded funds (ETFs) (the Underlying Funds), such fund indirectly bears its proportional share of the expenses of the Underlying Funds in addition to the direct expenses incurred presented in the table. These fees and expenses are not included in the annualized expense ratio used to calculate the expense estimate in the table below.

Hypothetical Example for Comparison Purposes

The second line of the accompanying table provides information about hypothetical account values and hypothetical expenses based on the actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds. If any fund is a shareholder of any Underlying Funds, such fund indirectly bears its proportional share of the expenses of the Underlying Funds in addition to the direct expenses as presented in the table. These fees and expenses are not included in the annualized expense ratio used to calculate the expense estimate in the table below.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transaction costs. Therefore, the second line of the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds.

	Annualized Expense Ratio-^A	Beginning Account Value November 1, 2020	Ending Account Value April 30, 2021	Expenses Paid During Period-^B November 1, 2020 to April 30, 2021
Fidelity Treasury Only Money Market Fund	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**

^A Annualized expense ratio reflects expenses net of applicable fee waivers.

^B Expenses are equal to the annualized expense ratio, multiplied by the average account value over the period, multiplied by 181/ 365 (to reflect the one-half year period). The fees and expenses of any Underlying Funds are not included in each annualized expense ratio.

^C 5% return per year before expenses

** If certain fees were not voluntarily waived by the investment adviser or its affiliates during the period, the annualized expense ratio would have been .42% and the expenses paid in the actual and hypothetical examples above would have been $2.08 and $2.11, respectively.

Distributions (Unaudited)

A total of 100% of the dividends distributed during the fiscal year was derived from interest on U.S. Government securities which is generally exempt from state income tax.

The fund designates $7,997,980 of distributions paid in the calendar year 2020 as qualifying to be taxed as interest-related dividends for nonresident alien shareholders.

The fund designates $8,035,988 of distributions paid in the calendar year 2020 as qualifying to be taxed as section 163(j) interest dividends.

The fund will notify shareholders in January 2022 of amounts for use in preparing 2021 income tax returns.

Fidelity Investments

TMM-ANN-0621
1.703531.123

Fidelity® Money Market Fund

Annual Report

April 30, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Report of Independent Registered Public Accounting Firm
Trustees and Officers
Shareholder Expense Example
Distributions

You may also call 1-800-544-8544 to request a free copy of the proxy voting guidelines.

Standard & Poor's, S&P and S&P 500 are registered service marks of The McGraw-Hill Companies, Inc. and have been licensed for use by Fidelity Distributors Corporation.

Other third-party marks appearing herein are the property of their respective owners.

NOT FDIC INSURED •MAY LOSE VALUE •NO BANK GUARANTEE

Neither the Fund nor Fidelity Distributors Corporation is a bank.

Note to Shareholders:

Investment Summary/Performance (Unaudited)

Effective Maturity Diversification

Days	% of fund's investments 4/30/21
1 - 7	40.2
8 - 30	14.6
31 - 60	29.2
61 - 90	5.9
91 - 180	10.1

Effective maturity is determined in accordance with the requirements of Rule 2a-7 under the Investment Company Act of 1940.

Asset Allocation (% of fund's net assets)

As of April 30, 2021
	Certificates of Deposit	12.7%
	Commercial Paper	41.2%
	Variable Rate Demand Notes (VRDNs)	0.1%
	U.S. Treasury Debt	5.1%
	Non-Negotiable Time Deposit	7.8%
	Other Instruments	0.5%
	Other Municipal Security	0.1%
	Repurchase Agreements	32.6%
	Net Other Assets (Liabilities)^*	(0.1)%

* Net Other Assets (Liabilities) are not included in the pie chart.

Current 7-Day Yields

	4/30/21
Fidelity® Money Market Fund	0.01%
Premium Class	0.01%

Schedule of Investments April 30, 2021

Showing Percentage of Net Assets

Certificate of Deposit - 12.7%
	Yield(a)	Principal Amount (000s)	Value (000s)
Domestic Certificates Of Deposit - 0.3%
Bank of America NA
10/19/21	0.19%	$128,000	$128,000
New York Branch, Yankee Dollar, Foreign Banks - 12.4%
Bank of Montreal
5/3/21 to 9/13/21	0.20 to 0.25	743,000	743,000
Bank of Nova Scotia
6/10/21 to 6/21/21	0.25	863,000	863,000
Bayerische Landesbank
5/4/21 to 6/4/21	0.16	423,000	423,000
Credit Agricole CIB
6/16/21 to 9/2/21	0.15 to 0.16	846,000	846,000
DZ BANK AG
6/15/21 to 6/30/21	0.15	254,000	254,000
Landesbank Baden-Wuerttemberg New York Branch
5/10/21 to 5/17/21	0.15	526,000	526,000
Mizuho Corporate Bank Ltd.
6/10/21	0.17	417,000	417,000
Sumitomo Mitsui Banking Corp.
8/2/21	0.17	213,000	213,000
Sumitomo Mitsui Trust Bank Ltd.
6/8/21 to 7/13/21	0.16 to 0.17	505,000	505,000
Toronto-Dominion Bank
6/8/21	0.25	100,000	100,000
			4,890,000
TOTAL CERTIFICATE OF DEPOSIT
(Cost $5,018,000)			5,018,000

Financial Company Commercial Paper - 39.9%
Bank of Nova Scotia
6/8/21 to 6/28/21	0.25 to 0.26	857,000	856,710
Barclays Bank PLC/Barclays U.S. CCP Funding LLC
5/11/21 to 6/4/21	0.22 (b)	413,000	412,944
Bayerische Landesbank
5/28/21	0.16	215,000	214,974
BNP Paribas Fortis
6/15/21	0.15	103,000	102,981
BNP Paribas SA
5/12/21 to 7/12/21	0.15 to 0.16	1,103,000	1,102,834
BofA Securities, Inc.
6/14/21 to 6/28/21	0.15 to 0.16	415,000	414,907
BPCE SA
5/12/21 to 6/3/21	0.15 to 0.16	1,242,000	1,241,922
Caisse d'Amort de la Dette Sociale
7/6/21 to 7/29/21	0.16(b)	1,071,000	1,070,661
Canadian Imperial Bank of Commerce
6/9/21 to 10/20/21	0.19 to 0.25	849,000	848,499
Citigroup Global Markets, Inc.
7/30/21	0.19	216,000	215,897
Credit Suisse AG
5/24/21 to 6/25/21	0.17 to 0.18	1,411,000	1,410,689
Federation des caisses Desjardin
6/9/21	0.15	51,000	50,992
ING U.S. Funding LLC
6/3/21	0.15	55,000	54,992
8/10/21	0.15	274,000	273,885
J.P. Morgan Securities, LLC
6/22/21	0.26	43,000	42,984
KfW
6/18/21 to 6/21/21	0.15	332,000	331,932
Landesbank Baden-Wurttemberg
5/3/21	0.07	206,000	205,999
Lloyds Bank PLC
5/18/21 to 7/26/21	0.15 to 0.17	1,144,000	1,143,727
Mitsubishi UFJ Trust & Banking Corp.
6/30/21 to 8/25/21	0.18 to 0.20	567,000	566,733
Mizuho Bank Ltd. Singapore Branch
5/18/21 to 7/30/21	0.18 to 0.19	749,000	748,836
Natexis Banques Populaires New York Branch
5/26/21	0.15	292,000	291,970
National Bank of Canada
5/10/21 to 10/4/21	0.15 to 0.25	820,425	820,135
Royal Bank of Canada
6/9/21 to 9/13/21	0.20 to 0.25	1,060,000	1,059,506
Skandinaviska Enskilda Banken AB
6/21/21 to 6/23/21	0.15	833,000	832,820
Sumitomo Mitsui Trust Bank Ltd.
6/14/21 to 6/25/21	0.17 to 0.19	851,000	850,795
The Toronto-Dominion Bank
6/8/21 to 9/16/21	0.20 to 0.25	184,000	183,899
UBS AG London Branch
9/1/21 to 9/16/21	0.20 to 0.21	394,000	393,693
TOTAL FINANCIAL COMPANY COMMERCIAL PAPER
(Cost $15,745,916)			15,745,916

Asset Backed Commercial Paper - 1.3%
Atlantic Asset Securitization Corp. (Liquidity Facility Credit Agricole CIB)

6/8/21	0.15	33,000	32,995
7/21/21	0.17	19,000	18,993
7/7/21	0.16	43,000	42,987
Gotham Funding Corp. (Liquidity Facility Bank of Tokyo-Mitsubishi UFJ Ltd.)

6/22/21	0.16	20,000	19,995
6/23/21	0.16	24,000	23,994
Manhattan Asset Funding Co. LLC (Liquidity Facility Sumitomo Mitsui Banking Corp.)

5/10/21	0.15	12,000	12,000
6/17/21	0.16	63,000	62,987
6/3/21	0.15	57,000	56,992
6/7/21	0.15	61,000	60,991
6/7/21	0.15	15,000	14,998
Sheffield Receivables Corp. (Liquidity Facility Barclays Bank PLC)

5/18/21	0.15	20,000	19,999
5/21/21	0.15	20,000	19,998
6/14/21	0.16	39,660	39,652
6/16/21	0.16	45,600	45,591
6/21/21	0.16	31,000	30,993
6/3/21	0.15	31,000	30,996
TOTAL ASSET BACKED COMMERCIAL PAPER
(Cost $534,161)			534,161

U.S. Treasury Debt - 5.1%
U.S. Treasury Obligations - 5.1%
U.S. Treasury Bills
5/4/21 to 8/5/21	0.07 to 0.11	1,936,700	1,936,629
U.S. Treasury Notes
10/31/21	0.32 (c)(d)	84,000	84,008
TOTAL U.S. TREASURY DEBT
(Cost $2,020,637)			2,020,637

Other Instrument - 0.5%
Master Notes - 0.5%
Toyota Motor Credit Corp.
5/7/21
(Cost $194,000)	0.34 (c)(d)(e)	194,000	194,000

Variable Rate Demand Note - 0.1%
Florida - 0.1%
Florida Timber Fin. III LLC Taxable Series 2008, LOC Wells Fargo Bank NA, VRDN
5/7/21
(Cost $40,000)	0.11 (c)	40,000	40,000

Non-Negotiable Time Deposit - 7.8%
Time Deposits - 7.8%
Barclays Bank PLC
5/3/21	0.15	1,567,000	1,567,000
Landesbank Hessen-Thuringen London Branch
5/4/21 to 5/7/21	0.12	1,014,000	1,014,000
Mizuho Bank Ltd.
5/3/21	0.05	297,000	297,000
Mizuho Bank Ltd. Canada Branch
5/3/21	0.05	200,000	200,000
TOTAL NON-NEGOTIABLE TIME DEPOSIT
(Cost $3,078,000)			3,078,000

Interfund Loans – 0.0%
	Principal Amount (000s)	Value (000s)
With:
Fidelity Small Cap Growth Fund K6, at 0.29% due 5/3/21(f)
(Cost $5,853)	$5,853	$5,853

Other Municipal Security - 0.1%
Other Municipal Security - 0.1%
Massachusetts Gen. Oblig. RAN Series C, 0.2473% 6/17/21
(Cost $43,825)	$43,825	$43,825
	Maturity Amount (000s)	Value (000s)

U.S. Government Agency Repurchase Agreement - 10.5%
In a joint trading account at 0.01% dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations) #	3,645,426	3,645,423
With:
ABN AMRO Bank NV at 0.02%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $135,660,310, 0.13% - 3.13%, 1/31/23 - 5/15/29)	133,000	133,000
Barclays Bank PLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $30,600,026, 2.00%, 4/1/41)	30,000	30,000
Goldman Sachs & Co. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $75,480,063, 1.78% - 6.00%, 11/20/23 - 4/15/61)	74,000	74,000
Morgan Stanley & Co., LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $90,780,076, 2.00% - 4.50%, 1/1/36 - 5/1/51)	89,000	89,000
TD Securities (U.S.A.) at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $180,540,244, 1.13% - 2.25%, 4/30/22 - 2/15/31)	177,000	177,000
TOTAL U.S. GOVERNMENT AGENCY REPURCHASE AGREEMENT
(Cost $4,148,423)		4,148,423

U.S. Treasury Repurchase Agreement - 12.8%
With:
ABN AMRO Bank NV at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $107,100,171, 1.50%, 8/15/26)	105,000	105,000
Barclays Bank PLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $395,760,394, 0.75%, 4/30/26)	388,000	388,000
Commerz Markets LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $333,540,356, 0.00% - 2.88%, 10/7/21 - 2/15/31)	327,000	327,000
Federal Reserve Bank of New York at 0%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $2,837,000, 1.63% - 2.75%, 9/30/26)	2,837,000	2,837,000
Fixed Income Clearing Corp. - BNYM at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $84,660,081, 1.25%, 3/31/28)	83,000	83,000
Fixed Income Clearing Corp. - SSB at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $169,356,582, 1.25%, 4/30/28)	166,000	166,000
ING Financial Markets LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $221,372,351, 1.38% - 2.88%, 4/30/22 - 12/31/26)	217,000	217,000
Natixis SA at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $140,796,431, 0.17% - 2.88%, 1/31/22 - 5/15/50)	138,000	138,000
SMBC Nikko Securities America, Inc. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $785,266,582, 0.13% - 3.13%, 1/31/23 - 11/15/28)	770,001	770,000
TD Securities (U.S.A.) at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $27,810,090, 2.88% - 3.00%, 5/15/43 - 2/15/47)	27,000	27,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $5,058,000)		5,058,000

Other Repurchase Agreement - 9.3%
Other Repurchase Agreement - 9.3%
With:
BMO Capital Markets Corp. at:
0.19%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $91,351,854, 1.85% - 5.75%, 11/1/23 - 4/22/42)	87,001	87,000
0.26%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $93,962,056)	87,002	87,000
0.29%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $93,721,143, 2.65% - 8.50%, 4/21/23 - 3/22/51)	87,002	87,000
BNP Paribas Prime Brokerage, Inc. at:
0.35%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $413,652,067)	383,011	383,000
0.44%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $182,526,694)	169,006	169,000
0.57%, dated 4/20/21 due 6/4/21 (Collateralized by Equity Securities valued at $230,087,926)(c)(d)(g)	213,209	213,000
BofA Securities, Inc. at:
0.73%, dated 4/26/21 due 8/3/21 (Collateralized by Equity Securities valued at $114,496,253)	106,271	106,000
0.78%, dated 4/23/21 due 8/3/21 (Collateralized by Equity Securities valued at $114,504,810)	106,413	106,000
Citigroup Global Markets, Inc. at:
0.69%, dated 1/22/21 due 5/21/21 (Collateralized by Corporate Obligations valued at $88,491,072, 0.00% - 14.05%, 5/5/21 - 8/1/19)	85,194	85,000
0.7%, dated 2/2/21 due 6/21/21 (Collateralized by Corporate Obligations valued at $68,156,803, 0.18% - 5.93%, 3/29/29 - 6/25/47)	63,170	63,000
ING Financial Markets LLC at 0.3%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $45,361,135)	42,001	42,000
J.P. Morgan Securities, LLC at:
0.35%, dated 4/26/21 due 6/4/21 (Collateralized by Equity Securities valued at $172,811,905)(c)(d)(g)	160,093	160,000
0.4%, dated:
4/12/21 due 6/4/21 (Collateralized by Equity Securities valued at $216,051,421)(c)(d)(g)	200,133	200,000
4/26/21 due 6/4/21 (Collateralized by Corporate Obligations valued at $254,900,046, 0.00% - 6.13%, 8/15/23 - 5/1/26)(c)(d)(g)	236,157	236,000
Mitsubishi UFJ Securities (U.S.A.), Inc. at:
0.3%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $114,482,862)	106,003	106,000
0.33%, dated:
4/28/21 due 5/5/21 (Collateralized by Equity Securities valued at $10,800,503)	10,001	10,000
4/29/21 due 5/6/21 (Collateralized by Equity Securities valued at $32,401,193)	30,002	30,000
0.57%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $8,459,396, 0.00% - 3.25%, 3/1/25 - 5/1/27)	8,000	8,000
Mizuho Securities U.S.A., Inc. at:
0.39%, dated 4/30/21 due 5/3/21 (Collateralized by Equity Securities valued at $114,483,738)	106,003	106,000
0.65%, dated 2/12/21 due 5/24/21 (Collateralized by Corporate Obligations valued at $45,216,279, 0.41% - 8.10%, 8/15/21 - 6/15/51)	43,078	43,000
Morgan Stanley & Co., Inc. at 0.42%, dated 4/13/21 due 6/14/21 (Collateralized by Equity Securities valued at $106,507,050)	100,072	100,000
RBS Securities, Inc. at 0.32%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $108,573,964, 0.00% - 6.12%, 5/24/21 - 8/15/49)	106,003	106,000
Societe Generale at:
0.26%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $228,785,412, 2.25% - 13.00%, 6/1/21 - 2/1/61)	212,005	212,000
0.31%, dated 4/27/21 due 5/4/21 (Collateralized by Corporate Obligations valued at $137,094,011, 2.25% - 12.50%, 9/15/21 - 10/15/93)	127,008	127,000
0.37%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $91,698,210, 0.00% - 13.00%, 9/15/21 - 10/22/90)	85,003	85,000
0.41%, dated 4/27/21 due 5/4/21 (Collateralized by Corporate Obligations valued at $45,323,565, 0.00% - 11.50%, 6/1/21 - 6/13/50)	42,003	42,000
Wells Fargo Securities, LLC at:
0.45%, dated 4/30/21 due 5/3/21 (Collateralized by Corporate Obligations valued at $22,681,682, 0.00%, 1/15/25 - 3/15/28)	21,001	21,000
0.48%, dated 4/29/21 due 5/6/21 (Collateralized by Corporate Obligations valued at $45,363,844, 0.00% - 1.00%, 12/1/24 - 2/1/26)	42,004	42,000
0.75%, dated 3/19/21 due 6/15/21 (Collateralized by Corporate Obligations valued at $138,370,082, 0.50% - 6.50%, 5/15/23 - 5/15/25)	128,235	128,000
0.78%, dated 3/9/21 due 6/7/21 (Collateralized by Corporate Obligations valued at $254,102,445, 0.38% - 4.25%, 1/15/23 - 6/15/27)	235,458	235,000
0.8%, dated:
2/8/21 due 5/7/21 (Collateralized by Corporate Obligations valued at $138,498,971, 0.13% - 1.13%, 5/15/23 - 3/1/25)	128,250	128,000
2/10/21 due 5/11/21 (Collateralized by Corporate Obligations valued at $115,771,572, 0.00% - 4.25%, 6/1/24 - 3/1/37)	107,214	107,000
(Cost $3,660,000)		3,660,000
TOTAL INVESTMENT IN SECURITIES - 100.1%
(Cost $39,546,815)		39,546,815
NET OTHER ASSETS (LIABILITIES) - (0.1)%		(56,687)
NET ASSETS - 100%		$39,490,128

Security Type Abbreviations

VRDN – VARIABLE RATE DEMAND NOTE (A debt instrument that is payable upon demand, either daily, weekly or monthly)

Legend

(a) Yield represents either the annualized yield at the date of purchase, or the stated coupon rate, or, for floating and adjustable rate securities, the rate at period end.

(b) Security exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be resold in transactions exempt from registration, normally to qualified institutional buyers. At the end of the period, the value of these securities amounted to $1,483,605,000 or 3.8% of net assets.

(d) Coupon is indexed to a floating interest rate which may be multiplied by a specified factor and/or subject to caps or floors.

(e) Restricted securities (including private placements) - Investment in securities not registered under the Securities Act of 1933 (excluding 144A issues). At the end of the period, the value of restricted securities (excluding 144A issues) amounted to $194,000,000 or 0.5% of net assets.

(f) Loan is with an affiliated fund.

(g) The maturity amount is based on the rate at period end.

Additional information on each restricted holding is as follows:

Security	Acquisition Date	Cost
Toyota Motor Credit Corp. 0.34%, 5/7/21	11/30/20	$194,000,000

Investment Valuation

Other Information

# Additional information on each counterparty to the repurchase agreement is as follows:

Repurchase Agreement / Counterparty	Value (000s)
$3,645,423,000 due 5/03/21 at 0.01%
BNY Mellon Capital Markets LLC	$222,380
Bank Of America, N.A.	213,608
Bofa Secs Inc	265,042
Citibank NA	59,344
Citigroup Global Markets, Inc.	89,015
Credit Agricole CIB New York Branch	285,691
HSBC Securities (USA), Inc.	20,770
ING Financial Markets LLC	16,601
Mitsubishi Ufj Secs Hldgs Ltd	151,287
Mizuho Securities USA, Inc.	14,836
Nomura Securities Internationa	404,870
RBC Dominion Securities, Inc.	551,852
Societe Generale	114,681
Sumitomo Mitsu Bk Corp Ny (DI)	751,116
Sumitomo Mitsui Bk Corp (REPO)	468,813
Wells Fargo Securities LLC	15,517
	$3,645,423

See accompanying notes which are an integral part of the financial statements.

Financial Statements

Statement of Assets and Liabilities

Amounts in thousands (except per-share amounts)		April 30, 2021
Assets
Investment in securities, at value (including repurchase agreements of $12,866,423) — See accompanying schedule: Unaffiliated issuers (cost $39,540,962)	$39,540,962
Affiliated issuers (cost $5,853)	5,853
Total Investment in Securities (cost $39,546,815)		$39,546,815
Receivable for fund shares sold		24,412
Interest receivable		3,621
Prepaid expenses		20
Receivable from investment adviser for expense reductions		1,788
Other receivables		313
Total assets		39,576,969
Liabilities
Payable to custodian bank	$14
Payable for fund shares redeemed	79,107
Distributions payable	25
Accrued management fee	7,079
Other affiliated payables	143
Other payables and accrued expenses	473
Total liabilities		86,841
Net Assets		$39,490,128
Net Assets consist of:
Paid in capital		$39,490,002
Total accumulated earnings (loss)		126
Net Assets		$39,490,128
Net Asset Value and Maximum Offering Price
Fidelity Money Market Fund:
Net Asset Value, offering price and redemption price per share ($4,430,334 ÷ 4,430,079 shares)		$1.00
Premium Class:
Net Asset Value, offering price and redemption price per share ($35,059,794 ÷ 35,057,038 shares)		$1.00

See accompanying notes which are an integral part of the financial statements.

Statement of Operations

Amounts in thousands		Year ended April 30, 2021
Investment Income
Interest (including $115 from affiliated interfund lending)		$134,927
Expenses
Management fee	$121,155
Transfer agent fees	51,818
Accounting fees and expenses	1,880
Custodian fees and expenses	420
Independent trustees' fees and expenses	155
Registration fees	547
Audit	45
Legal	69
Miscellaneous	159
Total expenses before reductions	176,248
Expense reductions	(64,323)
Total expenses after reductions		111,925
Net investment income (loss)		23,002
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers	8
Total net realized gain (loss)		8
Net increase in net assets resulting from operations		$23,010

See accompanying notes which are an integral part of the financial statements.

Statement of Changes in Net Assets

Amounts in thousands	Year ended April 30, 2021	Year ended April 30, 2020
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$23,002	$834,183
Net realized gain (loss)	8	79
Net increase in net assets resulting from operations	23,010	834,262
Distributions to shareholders	(23,003)	(834,183)
Share transactions - net increase (decrease)	(15,172,893)	12,485,517
Total increase (decrease) in net assets	(15,172,886)	12,485,596
Net Assets
Beginning of period	54,663,014	42,177,418
End of period	$39,490,128	$54,663,014

See accompanying notes which are an integral part of the financial statements.

Financial Highlights

Fidelity Money Market Fund

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.016	.020	.011	.005
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–	.016	.020	.011	.005
Distributions from net investment income	–^A	(.016)	(.020)	(.011)	(.005)
Total distributions	–^A	(.016)	(.020)	(.011)	(.005)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.02%	1.61%	2.03%	1.11%	.52%
Ratios to Average Net Assets^C
Expenses before reductions	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.25%	.42%	.42%	.42%	.42%
Expenses net of all reductions	.25%	.42%	.42%	.42%	.42%
Net investment income (loss)	.03%	1.56%	2.06%	1.15%	.55%
Supplemental Data
Net assets, end of period (in millions)	$4,430	$6,093	$5,196	$3,209	$2,301

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^C Expense ratios reflect operating expenses of the class. Expenses before reductions do not reflect amounts reimbursed, waived, or reduced through arrangements with the investment adviser, brokerage services, or other offset arrangements, if applicable, and do not represent the amount paid by the class during periods when reimbursements, waivers or reductions occur.

See accompanying notes which are an integral part of the financial statements.

Fidelity Money Market Fund Premium Class

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.017	.021	.012	.006
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.017	.021	.012	.006
Distributions from net investment income	–^A	(.017)	(.021)	(.012)	(.006)
Total distributions	–^A	(.017)	(.021)	(.012)	(.006)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.05%	1.73%	2.16%	1.23%	.64%
Ratios to Average Net Assets^C
Expenses before reductions	.36%	.36%	.37%	.37%	.37%
Expenses net of fee waivers, if any	.23%	.30%	.30%	.30%	.30%
Expenses net of all reductions	.23%	.30%	.30%	.30%	.30%
Net investment income (loss)	.05%	1.68%	2.18%	1.27%	.67%
Supplemental Data
Net assets, end of period (in millions)	$35,060	$48,570	$36,981	$15,497	$7,317

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

See accompanying notes which are an integral part of the financial statements.

Notes to Financial Statements

For the period ended April 30, 2021
(Amounts in thousands except percentages)

1. Organization.

Fidelity Money Market Fund (the Fund) is a fund of Fidelity Hereford Street Trust (the Trust) and is authorized to issue an unlimited number of shares. The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Delaware statutory trust. The Fund offers Fidelity Money Market Fund and Premium Class shares, each of which has equal rights as to assets and voting privileges. Each class has exclusive voting rights with respect to matters that affect that class. Shares of the Fund are only available for purchase by retail shareholders

2. Significant Accounting Policies.

Investment Valuation. The Fund categorizes the inputs to valuation techniques used to value its investments into a disclosure hierarchy consisting of three levels as shown below:

Level 1 – quoted prices in active markets for identical investments
Level 2 – other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, etc.)
Level 3 – unobservable inputs (including the Fund's own assumptions based on the best information available)

Investment Transactions and Income. The net asset value per share for processing shareholder transactions is calculated as of the close of business of the New York Stock Exchange (NYSE), normally 4:00 p.m. Eastern time. Security transactions are accounted for as of trade date. Gains and losses on securities sold are determined on the basis of identified cost and include proceeds received from litigation. Interest income is accrued as earned and includes coupon interest and amortization of premium and accretion of discount on debt securities as applicable. The principal amount on inflation-indexed securities is periodically adjusted to the rate of inflation and interest is accrued based on the principal amount. The adjustments to principal due to inflation are reflected as increases or decreases to Interest in the accompanying Statement of Operations.

Class Allocations and Expenses. Investment income, realized and unrealized capital gains and losses, common expenses of a fund, and certain fund-level expense reductions, if any, are allocated daily on a pro-rata basis to each class based on the relative net assets of each class to the total net assets of a fund. Each class differs with respect to transfer agent fees incurred, as applicable. Certain expense reductions may also differ by class, if applicable. For the reporting period, the allocated portion of income and expenses to each class as a percent of its average net assets may vary due to the timing of recording these transactions in relation to fluctuating net assets of the classes. Expenses directly attributable to a fund are charged to that fund. Expenses attributable to more than one fund are allocated among the respective funds on the basis of relative net assets or other appropriate methods. Expenses included in the accompanying financial statements reflect the expenses of that fund and do not include any expenses associated with any underlying mutual funds or exchange-traded funds. Although not included in a fund's expenses, a fund indirectly bears its proportionate share of these expenses through the net asset value of each underlying mutual fund or exchange-traded fund. Expense estimates are accrued in the period to which they relate and adjustments are made when actual amounts are known.

Deferred Trustee Compensation. Under a Deferred Compensation Plan (the Plan) for certain Funds, certain independent Trustees have elected to defer receipt of a portion of their annual compensation. Deferred amounts are invested in affiliated mutual funds, are marked-to-market and remain in a fund until distributed in accordance with the Plan. The investment of deferred amounts and the offsetting payable to the Trustees presented below are included in the accompanying Statement of Assets and Liabilities in other receivables and other payables and accrued expenses, as applicable.

Fidelity Money Market Fund

$313

Distributions are declared and recorded daily and paid monthly from net investment income. Distributions from realized gains, if any, are declared and recorded on the ex-dividend date. Income and capital gain distributions are declared separately for each class. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from GAAP. In addition, the Fund claimed a portion of the payment made to redeeming shareholders as a distribution for income tax purposes.

Book-tax differences are primarily due to deferred trustees compensation.

As of period end, the cost and unrealized appreciation (depreciation) in securities for federal income tax purposes were as follows:

Gross unrealized appreciation	$–
Gross unrealized depreciation	–
Net unrealized appreciation (depreciation)	$–
Tax Cost	$39,546,815

The tax-based components of distributable earnings as of period end were as follows:

Undistributed ordinary income

$126

The tax character of distributions paid was as follows:

	April 30, 2021	April 30, 2020
Ordinary Income	$23,003	$ 834,183

Repurchase Agreements. Pursuant to an Exemptive Order issued by the Securities and Exchange Commission, funds and other registered investment companies having management contracts with Fidelity Management and Research Company LLC, or its affiliates are permitted to transfer uninvested cash balances into joint trading accounts which are then invested in repurchase agreements. Funds may also invest directly with institutions in repurchase agreements. Repurchase agreements may be collateralized by government or non-government securities. Upon settlement date, collateral is held in segregated accounts with custodian banks and may be obtained in the event of a default of the counterparty. The collateral balance is monitored on a daily basis to ensure it is at least equal to the principal amount of the repurchase agreement (including accrued interest). In the event of a default by the counterparty, realization of the collateral proceeds could be delayed, during which time the value of the collateral may decline.

Restricted Securities (including Private Placements). Funds may invest in securities that are subject to legal or contractual restrictions on resale. These securities generally may be resold in transactions exempt from registration or to the public if the securities are registered. Disposal of these securities may involve time-consuming negotiations and expense, and prompt sale at an acceptable price may be difficult. Information regarding restricted securities held at period end is included at the end of the Schedule of Investments, if applicable.

3. Fees and Other Transactions with Affiliates.

Management Fee and Expense Contract. Fidelity Management & Research Company LLC (the investment adviser) and its affiliates provide the Fund with investment management related services for which the Fund pays a monthly management fee that is based on an annual rate of .25% of the Fund's average net assets. Under the expense contract, total expenses of Fidelity Money Market Fund are limited to an annual rate of .42% of the class' average net assets, with certain exceptions.

Transfer Agent Fees. Fidelity Investments Institutional Operations Company LLC (FIIOC), an affiliate of the investment adviser, is the transfer, dividend disbursing and shareholder servicing agent for each class of the Fund. FIIOC receives asset-based fees with respect to each account. FIIOC pays for typesetting, printing and mailing of shareholder reports, except proxy statements. Premium Class pays a transfer agent fee equal to an annual rate of .10% of class-level average net assets.

Under the expense contract, Fidelity Money Market Fund will pay a portion of the transfer agent fee at an annual rate of up to .17% of class-level average net assets.

For the period, transfer agent fees for each class were as follows:

	Amount	% of Class-Level Average Net Assets
Fidelity Money Market Fund	$8,612	.16
Premium Class	43,206	.10
	$51,818

During the period, the investment adviser or its affiliates waived a portion of these fees.

Accounting Fees. Fidelity Service Company, Inc. (FSC), an affiliate of the investment adviser, maintains the Fund's accounting records. The accounting fee is based on the level of average net assets for each month. For the period, the fees were equivalent to the following annual rates:

	% of Average Net Assets
Fidelity Money Market Fund	–^(a)

(a) The fees were equivalent to less than .005%.

Interfund Lending Program. Pursuant to an Exemptive Order issued by the Securities and Exchange Commission (the SEC), the Fund, along with other registered investment companies having management contracts with Fidelity Management & Research Company LLC (FMR), or other affiliated entities of FMR, may participate in an interfund lending program. This program provides an alternative credit facility allowing the Fund to borrow from, or lend money to, other participating affiliated funds. Any open loans at period end are presented under the caption "Interfund Loans" in the Schedule of Investments with accrued interest included in Other affiliated receivables on the Statement of Assets and Liabilities. Activity in this program during the period for which loans were outstanding was as follows:

		Average Loan Balance	Weighted Average Interest Rate
Fidelity Money Market Fund	Lender	22,911	.32%

4. Expense Reductions.

The investment adviser contractually agreed to reimburse Premium Class to the extent annual operating expenses exceeded .30% of the average net assets. This reimbursement will remain in place through August 31, 2022. Some expenses, for example the compensation of the independent Trustees, and certain other expenses such as interest expense, are excluded from this reimbursement. During the period, this reimbursement reduced Premium Class' expenses by $24,263.

Through arrangements with the Fund's custodian and each class' transfer agent, credits realized as a result of certain uninvested cash balances were used to reduce the Fund's expenses. During the period, custodian credits reduced the Fund's expenses by $78.

Additionally, the investment adviser or its affiliates voluntarily agreed to waive certain fees in order to avoid a negative yield. Such arrangements may be discontinued by the investment adviser at any time. For the period, the amount of the waiver for each class was as follows:

Fidelity Money Market Fund	$8,833
Premium Class	31,149

5. Distributions to Shareholders.

Distributions to shareholders of each class were as follows:

	Year ended April 30, 2021	Year ended April 30, 2020
Distributions to shareholders
Fidelity Money Market Fund	$1,355	$89,701
Premium Class	21,648	744,482
Total	$23,003	$834,183

6. Share Transactions.

Share transactions for each class of shares at a $1.00 per share were as follows and may contain automatic conversions between classes or exchanges between affiliated funds:

	Shares	Shares	Dollars	Dollars
	Year ended April 30, 2021	Year ended April 30, 2020	Year ended April 30, 2021	Year ended April 30, 2020
Fidelity Money Market Fund
Shares sold	2,481,773	7,092,098	$2,481,773	$7,092,098
Reinvestment of distributions	1,248	81,987	1,248	81,987
Shares redeemed	(4,145,540)	(6,277,347)	(4,145,540)	(6,277,347)
Net increase (decrease)	(1,662,519)	896,738	$(1,662,519)	$896,738
Premium Class
Shares sold	17,649,816	54,365,984	$17,649,816	$54,365,984
Reinvestment of distributions	19,925	684,700	19,925	684,700
Shares redeemed	(31,180,115)	(43,461,905)	(31,180,115)	(43,461,905)
Net increase (decrease)	(13,510,374)	11,588,779	$(13,510,374)	$11,588,779

7. Other.

8. Coronavirus (COVID-19) Pandemic.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Fidelity Hereford Street Trust and Shareholders of Fidelity Money Market Fund

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities, including the schedule of investments, of Fidelity Money Market Fund (one of the funds constituting Fidelity Hereford Street Trust, referred to hereafter as the “Fund”) as of April 30, 2021, the related statement of operations for the year ended April 30, 2021, the statement of changes in net assets for each of the two years in the period ended April 30, 2021, including the related notes, and the financial highlights for each of the five years in the period ended April 30, 2021 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period ended April 30, 2021 and the financial highlights for each of the five years in the period ended April 30, 2021 in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of April 30, 2021 by correspondence with the custodians and brokers. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

June 14, 2021

We have served as the auditor of one or more investment companies in the Fidelity group of funds since 1932.

Trustees and Officers

The fund’s Statement of Additional Information (SAI) includes more information about the Trustees. To request a free copy, call Fidelity at 1-800-544-8544.

Interested Trustees*:

Correspondence intended for a Trustee who is an interested person may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Abigail P. Johnson (1961)

Year of Election or Appointment: 2009

Trustee

Chairman of the Board of Trustees

Jennifer Toolin McAuliffe (1959)

Year of Election or Appointment: 2016

Trustee

* Determined to be an “Interested Trustee” by virtue of, among other things, his or her affiliation with the trust or various entities under common control with FMR.

Independent Trustees:

Correspondence intended for an Independent Trustee may be sent to Fidelity Investments, P.O. Box 55235, Boston, Massachusetts 02205-5235.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Elizabeth S. Acton (1951)

Year of Election or Appointment: 2013

Trustee

Ann E. Dunwoody (1953)

Year of Election or Appointment: 2018

Trustee

John Engler (1948)

Year of Election or Appointment: 2014

Trustee

Robert F. Gartland (1951)

Year of Election or Appointment: 2010

Trustee

Arthur E. Johnson (1947)

Year of Election or Appointment: 2008

Trustee

Chairman of the Independent Trustees

Michael E. Kenneally (1954)

Year of Election or Appointment: 2009

Trustee

Vice Chairman of the Independent Trustees

Marie L. Knowles (1946)

Year of Election or Appointment: 2001

Trustee

Mark A. Murray (1954)

Year of Election or Appointment: 2016

Trustee

Advisory Board Members and Officers:

Correspondence intended for an officer may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210. Officers appear below in alphabetical order.

Name, Year of Birth; Principal Occupation

Robert W. Helm (1957)

Year of Election or Appointment: 2021

Member of the Advisory Board

Craig S. Brown (1977)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Brown also serves as Assistant Treasurer of other funds. Mr. Brown is an employee of Fidelity Investments (2013-present).

John J. Burke III (1964)

Year of Election or Appointment: 2018

Chief Financial Officer

David J. Carter (1973)

Year of Election or Appointment: 2020

Assistant Secretary

Mr. Carter also serves as Assistant Secretary of other funds. Mr. Carter serves as Vice President, Associate General Counsel (2010-present) and is an employee of Fidelity Investments (2005-present).

Jonathan Davis (1968)

Year of Election or Appointment: 2010

Assistant Treasurer

Laura M. Del Prato (1964)

Year of Election or Appointment: 2018

President and Treasurer

Colm A. Hogan (1973)

Year of Election or Appointment: 2016

Assistant Treasurer

Cynthia Lo Bessette (1969)

Year of Election or Appointment: 2019

Secretary and Chief Legal Officer (CLO)

Chris Maher (1972)

Year of Election or Appointment: 2013

Assistant Treasurer

Jamie Pagliocco (1964)

Year of Election or Appointment: 2020

Vice President

Kenneth B. Robins (1969)

Year of Election or Appointment: 2020

Chief Compliance Officer

Brett Segaloff (1972)

Year of Election or Appointment: 2021

Anti-Money Laundering (AML) Officer

Stacie M. Smith (1974)

Year of Election or Appointment: 2013

Assistant Treasurer

Marc L. Spector (1972)

Year of Election or Appointment: 2016

Deputy Treasurer

Jim Wegmann (1979)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Wegmann also serves as Assistant Treasurer of other funds. Mr. Wegmann is an employee of Fidelity Investments (2011-present).

Shareholder Expense Example

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (November 1, 2020 to April 30, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value November 1, 2020	Ending Account Value April 30, 2021	Expenses Paid During Period-^B November 1, 2020 to April 30, 2021
Fidelity Money Market Fund
Fidelity Money Market Fund	.19%
Actual		$1,000.00	$1,000.00	$.94**
Hypothetical-^C		$1,000.00	$1,023.85	$.95**
Premium Class	.19%
Actual		$1,000.00	$1,000.00	$.94**
Hypothetical-^C		$1,000.00	$1,023.85	$.95**

^A Annualized expense ratio reflects expenses net of applicable fee waivers.

^C 5% return per year before expenses

** If certain fees were not voluntarily waived by the investment adviser or its affiliates during the period, the annualized expense ratio and the expenses paid in the actual and hypothetical examples above would have been as shown in table below:

	Annualized Expense Ratio-^(a)	Expenses Paid
Fidelity Money Market Fund
Fidelity Money Market Fund	.42%
Actual		$2.08
Hypothetical-^(b)		$2.11
Premium Class	.30%
Actual		$1.49
Hypothetical-^(b)		$1.51

(a) Annualized expense ratio reflects expenses net of applicable fee waivers.

(b) 5% return per year before expenses

Distributions (Unaudited)

A total of 14.55% of the dividends distributed during the fiscal year was derived from interest on U.S. Government securities which is generally exempt from state income tax.

The fund designates $108,674,986 of distributions paid in the calendar year 2020 as qualifying to be taxed as interest-related dividends for nonresident alien shareholders.

The fund designates $228,249,965 of distributions paid in the calendar year 2020 as qualifying to be taxed as section 163(j) interest dividends.

The fund will notify shareholders in January 2022 of amounts for use in preparing 2021 income tax returns.

Fidelity Investments

SPM-ANN-0621
1.703534.123

Fidelity® Government Money Market Fund

Annual Report

April 30, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Report of Independent Registered Public Accounting Firm
Trustees and Officers
Shareholder Expense Example
Distributions

You may also call 1-800-544-8544 if you’re an individual investing directly with Fidelity, call 1-800-835-5092 if you’re a plan sponsor or participant with Fidelity as your recordkeeper or call 1-877-208-0098 on institutional accounts or if you’re an advisor or invest through one to request a free copy of the proxy voting guidelines.

Standard & Poor's, S&P and S&P 500 are registered service marks of The McGraw-Hill Companies, Inc. and have been licensed for use by Fidelity Distributors Corporation.

Other third-party marks appearing herein are the property of their respective owners.

NOT FDIC INSURED •MAY LOSE VALUE •NO BANK GUARANTEE

Neither the Fund nor Fidelity Distributors Corporation is a bank.

Note to Shareholders:

Investment Summary/Performance (Unaudited)

Effective Maturity Diversification

Days	% of fund's investments 4/30/21
1 - 7	52.9
8 - 30	12.7
31 - 60	12.0
61 - 90	7.4
91 - 180	12.8
> 180	2.2

Effective maturity is determined in accordance with the requirements of Rule 2a-7 under the Investment Company Act of 1940.

Asset Allocation (% of fund's net assets)

As of April 30, 2021
	U.S. Treasury Debt	43.8%
	U.S. Government Agency Debt	19.5%
	Repurchase Agreements	37.6%
	Variable Rate Demand Notes (VRDNs)	0.1%
	Net Other Assets (Liabilities)^*	(1.0)%

* Net Other Assets (Liabilities) are not included in the pie chart

Current 7-Day Yields

	4/30/21
Capital Reserves Class	0.01%
Daily Money Class	0.01%
Advisor M Class	0.01%
Fidelity Government Money Market Fund	0.01%
Premium Class	0.01%
Class K6	0.01%

Schedule of Investments April 30, 2021

Showing Percentage of Net Assets

U.S. Treasury Debt - 43.8%
	Yield(a)	Principal Amount	Value
U.S. Treasury Obligations - 43.8%
U.S. Treasury Bills
5/4/21 to 12/2/21	0.01 to 0.13%	$78,648,519,700	$78,640,773,373
U.S. Treasury Bonds
5/15/21 to 11/15/21	0.04 to 0.12	372,800,000	380,597,757
U.S. Treasury Notes
5/15/21 to 1/31/23	0.01 to 0.32 (b)	17,982,187,700	18,072,893,452
TOTAL U.S. TREASURY DEBT
(Cost $97,094,264,582)			97,094,264,582

Variable Rate Demand Note - 0.1%
California - 0.0%
FHLMC California Statewide Cmntys. Dev. Auth. Multi-family Hsg. Rev. (Heritage Park Apts. Proj.) Series 2008 C, 0.05% 5/7/21, LOC Freddie Mac, VRDN
5/7/21	0.05 (b)(c)	9,700,000	9,700,000
FHLMC Los Angeles Cmnty. Redev. Agcy. Multi-family Hsg. Rev. (Grand Promenade Proj.) Series 2002, 0.08% 5/7/21, LOC Freddie Mac, VRDN
5/7/21	0.08 (b)	41,100,000	41,100,000
			50,800,000
New York - 0.1%
FHLMC New York Hsg. Fin. Agcy. Rev. (Clinton Green North Hsg. Proj.) Series 2005 A, 0.06% 5/7/21, LOC Freddie Mac, VRDN
5/7/21	0.06 (b)(c)	35,445,000	35,445,000
FHLMC New York Hsg. Fin. Agcy. Rev. (Clinton Green South Hsg. Proj.) Series 2005 A, 0.06% 5/7/21, LOC Freddie Mac, VRDN
5/7/21	0.06 (b)(c)	16,900,000	16,900,000
FHLMC New York Hsg. Fin. Agcy. Rev. (Theatre Row Tower Hsg. Proj.) Series 2000 A, 0.06% 5/7/21, LOC Freddie Mac, VRDN
5/7/21	0.06 (b)(c)	17,500,000	17,500,000
FNMA New York City Hsg. Dev. Corp. Multi-family Rental Hsg. Rev. (155 West 21st Street Dev. Proj.) Series 2007 A, 0.06% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.06 (b)(c)	13,100,000	13,100,000
FNMA New York City Hsg. Dev. Corp. Multi-family Rental Hsg. Rev. (255 West 9th Street Proj.) Series 2001 A, 0.05% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.05 (b)(c)	24,800,000	24,800,000
FNMA New York Hsg. Fin. Agcy. Rev. (250 West 50th Street Hsg. Proj.) Series 1997 A, 0.05% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.05 (b)(c)	23,600,000	23,600,000
FNMA New York Hsg. Fin. Agcy. Rev. (316 Eleventh Ave. Hsg. Proj.) Series 2007 A, 0.06% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.06 (b)(c)	16,100,000	16,100,000
FNMA New York Hsg. Fin. Agcy. Rev. (600 West and 42nd St. Hsg. Proj.) Series 2007 A, 0.08% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.08 (b)(c)	48,350,000	48,350,000
FNMA New York Hsg. Fin. Agcy. Rev. (Tribeca Park Proj.) Series 1997 A, 0.06% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.06 (b)(c)	11,400,000	11,400,000
FNMA New York Hsg. Fin. Agcy. Rev. (West 23rd Street Hsg. Proj.) Series 2001 A, 0.05% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.05 (b)(c)	6,500,000	6,500,000
FNMA New York Hsg. Fin. Agcy. Rev. Series 1997 A, 0.06% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.06 (b)(c)	10,800,000	10,800,000
FNMA New York Hsg. Fin. Agcy. Rev. Series 2008 A, 0.08% 5/7/21, LOC Fannie Mae, VRDN
5/7/21	0.08 (b)(c)	15,200,000	15,200,000
			239,695,000
TOTAL VARIABLE RATE DEMAND NOTE
(Cost $290,495,000)			290,495,000

U.S. Government Agency Debt - 19.5%
Federal Agencies - 19.5%
Fannie Mae
6/4/21 to 7/29/22	0.09 to 0.36 (b)(d)	9,966,015,000	9,966,079,343
Federal Farm Credit Bank
5/3/21 to 3/25/22	0.01 to 0.20 (b)	1,357,250,000	1,357,128,340
Federal Home Loan Bank
5/3/21 to 12/15/22	0.01 to 0.25 (b)	26,051,954,000	26,053,728,761
Freddie Mac
6/24/21 to 9/9/22	0.10 to 0.33 (b)	5,797,800,000	5,797,832,742
TOTAL U.S. GOVERNMENT AGENCY DEBT
(Cost $43,174,769,186)			43,174,769,186

U.S. Government Agency Repurchase Agreement - 15.3%
	Maturity Amount	Value
In a joint trading account at:
0.01% dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations) #	$20,274,479,497	$20,274,463,000
0.01% dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations) #	47,783,040	47,783,000
With:
ABN AMRO Bank NV at 0.02%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $758,726,904, 0.38% - 5.50%, 8/31/23 - 4/20/51)	743,001,238	743,000,000
Barclays Bank PLC at 0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $450,840,877, 3.00% - 4.00%, 10/20/43 - 5/20/49)	442,000,859	442,000,000
4/27/21 due 5/4/21 (Collateralized by U.S. Government Obligations valued at $393,720,656, 3.00% - 4.50%, 10/20/46 - 10/20/49)	386,000,751	386,000,000
4/28/21 due 5/5/21 (Collateralized by U.S. Government Obligations valued at $156,060,218, 2.50%, 3/20/51)	153,000,298	153,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $169,320,142, 2.50%, 3/20/51)	166,000,138	166,000,000
BMO Harris Bank NA at:
0.03%, dated 4/1/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $195,845,223, 1.50% - 6.50%, 10/20/33 - 5/15/59)	192,005,120	192,000,000
0.05%, dated 4/12/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $97,922,856, 1.50% - 3.00%, 4/1/36 - 4/20/51)	96,012,133	96,000,000
0.07%, dated 2/5/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $76,512,942, 2.50% - 3.50%, 8/20/50 - 2/20/51)	75,013,271	75,000,000
CIBC Bank U.S.A. at 0.08%, dated 4/29/21 due 7/28/21 (Collateralized by U.S. Government Obligations valued at $78,549,453, 0.13% - 6.99%, 4/30/22 - 5/1/51)	77,015,400	77,000,000
Citibank NA at:
0.01%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Government Obligations valued at $98,213,191, 0.00% - 9.00%, 5/6/21 - 9/15/65)	96,000,187	96,000,000
0.02%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $590,584,208, 0.00% - 10.50%, 8/15/21 - 3/1/51)	579,002,252	579,000,000
Citigroup Global Capital Markets, Inc. at 0.02%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Government Obligations valued at $393,721,389, 1.50% - 7.00%, 5/1/36 - 2/15/41)	386,001,501	386,000,000
Deutsche Bank AG, New York at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $201,880,085, 3.25% - 3.80%, 5/15/43 - 11/15/46)	196,000,082	196,000,000
Deutsche Bank Securities, Inc. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $603,838,917, 2.00% - 6.00%, 8/1/29 - 1/15/56)	588,000,245	588,000,000
Goldman Sachs & Co. at 0.01%, dated:
4/29/21 due 5/6/21 (Collateralized by U.S. Government Obligations valued at $1,568,761,743, 1.50% - 6.50%, 12/20/24 - 9/15/59)	1,538,002,991	1,538,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $422,280,352, 1.25% - 6.00%, 5/20/27 - 12/15/55)	414,000,345	414,000,000
Mitsubishi UFJ Securities (U.S.A.), Inc. at:
0.04%, dated:
4/14/21 due 6/14/21 (Collateralized by U.S. Government Obligations valued at $196,864,156, 2.00% - 5.50%, 6/1/22 - 4/1/51)	193,013,081	193,000,000
4/19/21 due 6/18/21 (Collateralized by U.S. Government Obligations valued at $255,003,967, 1.74% - 6.00%, 9/1/21 - 5/1/51)	250,016,667	250,000,000
4/21/21 due 6/21/21 (Collateralized by U.S. Government Obligations valued at $294,783,931, 2.00% - 5.00%, 1/1/24 - 4/1/51)	289,019,588	289,000,000
0.06%, dated 4/6/21 due 6/7/21 (Collateralized by U.S. Government Obligations valued at $392,717,672, 1.46% - 5.54%, 1/1/24 - 5/1/51)	385,039,783	385,000,000
Morgan Stanley & Co., LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $505,920,800, 0.10% - 5.50%, 8/3/21 - 2/1/57)	496,000,413	496,000,000
Nomura Securities International, Inc. at 0.01%, dated 4/28/21 due 5/5/21 (Collateralized by U.S. Government Obligations valued at $510,000,709, 1.50% - 4.53%, 9/1/35 - 3/20/69)	500,000,972	500,000,000
RBC Dominion Securities at 0.06%, dated 3/22/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $393,548,398, 0.00% - 6.25%, 6/30/23 - 4/20/51)	385,119,350	385,000,000
RBC Financial Group at:
0.03%, dated:
3/18/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $980,257,575, 1.50% - 7.00%, 12/15/23 - 4/1/59)	961,073,677	961,000,000
3/19/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $981,276,797, 1.71% - 4.50%, 8/1/33 - 5/1/51)	962,076,158	962,000,000
3/22/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $1,002,702,670, 1.50% - 6.50%, 4/1/23 - 4/1/59)	983,075,363	983,000,000
3/23/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $211,147,215, 1.50% - 8.00%, 8/1/22 - 5/1/51)	207,015,870	207,000,000
0.08%, dated 2/9/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $194,348,420, 1.50% - 7.59%, 1/15/29 - 7/1/56)	189,074,760	189,000,000
Sumitomo Mitsui Trust Bank Ltd. at:
0.11%, dated 4/1/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $27,622,040, 0.38% - 3.50%, 3/31/22 - 1/20/42)	27,007,260	27,000,000
0.12%, dated:
3/16/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $120,537,188, 0.38% - 3.50%, 3/31/22 - 9/1/47)	118,042,087	118,000,000
3/22/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $189,991,258, 0.38% - 4.00%, 3/31/22 - 6/1/48)	186,071,300	186,000,000
3/29/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $199,973,061, 0.38% - 4.00%, 3/31/22 - 8/1/49)	196,082,320	196,000,000
TD Securities (U.S.A.) at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $1,012,860,844, 2.00% - 3.50%, 4/1/36 - 2/1/51)	993,000,828	993,000,000
TOTAL U.S. GOVERNMENT AGENCY REPURCHASE AGREEMENT
(Cost $33,769,246,000)		33,769,246,000

U.S. Treasury Repurchase Agreement - 22.3%
With:
ABN AMRO Bank NV at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $599,236,908, 0.13% - 5.50%, 1/31/23 - 8/15/45)	586,000,488	586,000,000
Barclays Bank PLC at 0.01%, dated:
4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $93,523,107, 0.25% - 2.50%, 8/31/25 - 5/15/46)	91,000,177	91,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $2,220,456,251, 0.13% - 8.00%, 11/15/21 - 2/15/46)	2,168,001,807	2,168,000,000
BNP Paribas, SA at:
0.02%, dated:
4/12/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $534,388,450, 0.00% - 6.75%, 7/15/21 - 8/15/50)	523,006,392	523,000,000
4/19/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $1,460,683,780, 0.00% - 7.25%, 5/20/21 - 5/15/50)	1,432,022,276	1,432,000,000
0.03%, dated:
4/5/21 due 5/5/21 (Collateralized by U.S. Treasury Obligations valued at $838,052,555, 0.00% - 8.00%, 5/6/21 - 5/15/50)	821,020,525	821,000,000
4/6/21 due 5/6/21 (Collateralized by U.S. Treasury Obligations valued at $1,856,235,307, 0.00% - 6.75%, 5/20/21 - 8/15/50)	1,817,045,425	1,817,000,000
4/8/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $1,846,343,993, 0.00% - 8.00%, 5/20/21 - 5/15/50)	1,808,048,213	1,808,000,000
4/9/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $982,527,703, 0.00% - 8.13%, 5/15/21 - 5/15/50)	961,025,627	961,000,000
0.05%, dated 3/2/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $2,181,818,316, 0.00% - 6.75%, 5/20/21 - 5/15/50)	2,135,183,847	2,135,000,000
CIBC Bank U.S.A. at 0.02%, dated:
4/13/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $356,257,946, 0.00% - 4.63%, 9/30/21 - 8/15/45)	349,006,786	349,000,000
4/20/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $355,985,340, 0.13% - 4.63%, 8/31/22 - 5/15/45)	349,006,786	349,000,000
4/22/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $248,918,629, 0.13% - 4.63%, 6/30/22 - 8/15/46)	244,004,744	244,000,000
Citigroup Global Capital Markets, Inc. at 0.03%, dated 4/22/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $539,647,121, 0.13% - 3.00%, 8/15/23 - 11/15/47)	524,013,973	524,000,000
Commerz Markets LLC at 0.01%, dated:
4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $947,747,820, 0.13% - 6.75%, 7/15/22 - 11/15/50)	929,001,806	929,000,000
4/28/21 due 5/5/21 (Collateralized by U.S. Treasury Obligations valued at $711,982,268, 0.13% - 6.75%, 7/15/22 - 11/15/50)	698,001,357	698,000,000
4/29/21 due 5/6/21 (Collateralized by U.S. Treasury Obligations valued at $355,997,153, 0.00% - 2.25%, 10/7/21 - 11/15/50)	349,000,679	349,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,865,619,110, 0.13% - 6.75%, 10/31/21 - 2/15/50)	1,828,001,523	1,828,000,000
Credit AG at:
0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $942,481,852, 0.25% - 2.13%, 1/31/22 - 5/15/25)	924,001,797	924,000,000
4/28/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $125,660,218, 2.25% - 3.63%, 8/15/43 - 8/15/49)	122,000,203	122,000,000
5/3/21 due 5/7/21(e)	697,000,774	697,000,000
0.02%, dated:
4/8/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,424,959,793, 0.50% - 2.38%, 8/31/24 - 8/15/30)	1,397,019,403	1,397,000,000
4/16/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $180,251,751, 3.38%, 5/15/44)	175,002,722	175,000,000
4/28/21 due 5/7/21
(Collateralized by U.S. Treasury Obligations valued at $357,735,908, 1.13% - 2.25%, 5/15/40 - 8/15/46)	349,005,623	349,000,000
(Collateralized by U.S. Treasury Obligations valued at $536,211,473, 2.75% - 4.50%, 8/15/39 - 2/15/48)	522,008,120	522,000,000
Deutsche Bank AG, New York at 0.01%, dated 4/30/21 due 5/3/21
(Collateralized by U.S. Treasury Obligations valued at $726,792,188, 0.13% - 4.50%, 5/15/21 - 11/15/46)	710,000,296	710,000,000
(Collateralized by U.S. Treasury Obligations valued at $909,791,160, 1.25% - 8.13%, 8/15/21 - 5/15/50)	887,000,370	887,000,000
DNB Bank ASA at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $542,640,562, 0.25% - 2.88%, 5/15/24 - 5/15/29)	532,000,443	532,000,000
Federal Reserve Bank of New York at 0%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $9,011,000,062, 2.50% - 2.63%, 8/15/23 - 2/15/29)	9,011,000,000	9,011,000,000
Fixed Income Clearing Corp. - BNYM at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $474,300,280, 0.13%, 4/30/23)	465,000,388	465,000,000
Fixed Income Clearing Corp. - SSB at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $947,784,688, 1.25%, 4/30/28)	929,000,774	929,000,000
ING Financial Markets LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,240,841,140, 1.25% - 2.88%, 4/30/22 - 5/15/29)	1,216,001,013	1,216,000,000
J.P. Morgan Securities, LLC at 0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $889,441,743, 0.00% - 3.00%, 8/19/21 - 1/31/26)	872,001,696	872,000,000
4/30/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $349,860,364, 2.50% - 2.88%, 8/15/21 - 5/15/24)	343,000,667	343,000,000
Lloyds Bank Corp. Markets PLC at:
0.05%, dated 3/26/21 due 6/28/21 (Collateralized by U.S. Treasury Obligations valued at $177,434,489, 0.63% - 0.75%, 12/31/27 - 1/31/28)	174,022,717	174,000,000
0.06%, dated 4/12/21 due 7/12/21 (Collateralized by U.S. Treasury Obligations valued at $177,493,356, 0.13% - 2.25%, 7/31/22 - 11/15/27)	174,026,390	174,000,000
0.09%, dated:
3/3/21 due 6/3/21 (Collateralized by U.S. Treasury Obligations valued at $139,806,149, 0.25% - 2.25%, 11/15/23 - 11/15/27)	137,031,510	137,000,000
3/10/21 due 6/10/21 (Collateralized by U.S. Treasury Obligations valued at $88,703,662, 2.25% - 2.88%, 10/31/23 - 11/15/27)	87,020,010	87,000,000
3/11/21 due 6/11/21 (Collateralized by U.S. Treasury Obligations valued at $141,759,646, 2.75%, 8/31/25)	139,031,970	139,000,000
Lloyds Bank PLC at:
0.05%, dated:
4/19/21 due 7/19/21 (Collateralized by U.S. Treasury Obligations valued at $178,418,455, 1.50% - 2.00%, 4/30/24 - 11/30/24)	175,022,118	175,000,000
4/26/21 due:
7/26/21 (Collateralized by U.S. Treasury Obligations valued at $177,503,283, 1.50% - 2.75%, 11/15/23 - 11/30/24)	174,021,992	174,000,000
7/27/21 (Collateralized by U.S. Treasury Obligations valued at $107,098,223, 1.50% - 1.63%, 11/15/22 - 11/30/24)	105,013,417	105,000,000
4/28/21 due 7/28/21 (Collateralized by U.S. Treasury Obligations valued at $177,456,414, 1.50% - 6.00%, 11/30/24 - 2/15/26)	174,021,992	174,000,000
0.06%, dated:
3/30/21 due 6/29/21 (Collateralized by U.S. Treasury Obligations valued at $177,494,598, 1.50% - 1.88%, 2/28/22 - 11/30/24)	174,026,390	174,000,000
3/31/21 due:
7/1/21 (Collateralized by U.S. Treasury Obligations valued at $123,398,146, 1.50% - 2.00%, 11/30/22 - 11/30/24)	121,018,553	121,000,000
7/2/21 (Collateralized by U.S. Treasury Obligations valued at $123,417,535, 6.00%, 2/15/26)	121,018,755	121,000,000
0.09%, dated:
2/16/21 due 5/17/21 (Collateralized by U.S. Treasury Obligations valued at $69,340,020, 1.50% - 2.00%, 4/30/24 - 11/30/24)	68,015,300	68,000,000
2/17/21 due 5/17/21 (Collateralized by U.S. Treasury Obligations valued at $105,029,563, 1.50% - 2.00%, 7/15/22 - 12/31/24)	103,022,918	103,000,000
2/19/21 due 5/19/21 (Collateralized by U.S. Treasury Obligations valued at $333,586,703, 1.50% - 2.75%, 3/15/22 - 2/28/25)	327,072,758	327,000,000
2/23/21 due 5/24/21 (Collateralized by U.S. Treasury Obligations valued at $139,721,579, 1.50% - 1.63%, 11/30/24 - 9/30/26)	137,030,825	137,000,000
0.1%, dated:
2/9/21 due 5/10/21 (Collateralized by U.S. Treasury Obligations valued at $192,781,994, 1.50% - 2.63%, 5/15/21 - 11/30/24)	189,047,250	189,000,000
2/10/21 due 5/11/21 (Collateralized by U.S. Treasury Obligations valued at $174,406,626, 1.50% - 2.63%, 5/15/21 - 11/30/24)	171,042,750	171,000,000
Mizuho Bank, Ltd. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $533,331,018, 2.38%, 5/15/29)	522,000,435	522,000,000
MUFG Securities EMEA PLC at:
0.01%, dated:
4/27/21 due:
5/3/21 (Collateralized by U.S. Treasury Obligations valued at $181,503,394, 2.00% - 3.13%, 10/31/22 - 8/15/44)	178,000,297	178,000,000
5/4/21 (Collateralized by U.S. Treasury Obligations valued at $316,109,531, 0.13% - 3.13%, 10/31/22 - 8/15/44)	310,000,603	310,000,000
4/28/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $927,845,337, 0.63% - 3.13%, 4/30/24 - 8/15/44)	910,001,517	910,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $2,467,337,351, 0.13% - 2.25%, 4/30/23 - 2/15/41)	2,419,002,016	2,419,000,000
5/3/21 due 5/7/21(e)	404,000,786	404,000,000
0.02%, dated 4/26/21 due 5/5/21 (Collateralized by U.S. Treasury Obligations valued at $763,733,247, 1.13% - 3.13%, 8/31/21 - 5/15/48)	749,003,745	749,000,000
Natixis SA at:
0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $786,420,722, 0.07% - 2.63%, 7/15/21 - 8/15/30)	771,000,643	771,000,000
0.02%, dated 4/16/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $712,038,466, 0.00% - 7.63%, 5/11/21 - 2/15/51)	698,014,736	698,000,000
Norinchukin Bank at:
0.06%, dated:
4/9/21 due 7/9/21 (Collateralized by U.S. Treasury Obligations valued at $294,790,415, 2.38%, 5/15/27)	289,043,832	289,000,000
4/12/21 due 7/12/21 (Collateralized by U.S. Treasury Obligations valued at $213,186,500, 2.00%, 11/15/26)	209,031,698	209,000,000
4/13/21 due 7/13/21 (Collateralized by U.S. Treasury Obligations valued at $177,485,143, 2.00%, 11/15/26)	174,026,390	174,000,000
0.09%, dated:
2/12/21 due 5/12/21 (Collateralized by U.S. Treasury Obligations valued at $175,473,864, 2.00%, 11/15/26)	172,038,270	172,000,000
2/18/21 due 5/18/21 (Collateralized by U.S. Treasury Obligations valued at $175,471,173, 1.50% - 2.38%, 8/15/26 - 5/15/27)	172,038,270	172,000,000
2/19/21 due 5/19/21 (Collateralized by U.S. Treasury Obligations valued at $139,764,534, 2.00%, 11/15/26)	137,030,483	137,000,000
2/22/21 due 5/21/21 (Collateralized by U.S. Treasury Obligations valued at $254,022,631, 2.00%, 11/15/26)	249,054,780	249,000,000
2/24/21 due 5/24/21 (Collateralized by U.S. Treasury Obligations valued at $175,468,548, 2.75%, 6/30/25)	172,038,270	172,000,000
3/3/21 due 6/3/21 (Collateralized by U.S. Treasury Obligations valued at $87,732,798, 1.50% - 2.38%, 8/15/26 - 5/15/27)	86,019,780	86,000,000
SMBC Nikko Securities America, Inc. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $785,248,103, 2.13% - 2.75%, 12/31/22 - 11/15/23)	770,000,642	770,000,000
Societe Generale at 0.01%, dated 4/29/21 due 5/6/21
(Collateralized by U.S. Treasury Obligations valued at $177,561,466, 0.00% - 6.25%, 5/31/21 - 11/15/48)	174,000,338	174,000,000
(Collateralized by U.S. Treasury Obligations valued at $177,481,561, 0.00% - 6.75%, 5/13/21 - 11/15/48)	174,000,338	174,000,000
TD Securities (U.S.A.) at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $157,080,195, 0.13% - 2.25%, 5/31/22 - 8/15/30)	154,000,128	154,000,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $49,406,000,000)		49,406,000,000
TOTAL INVESTMENT IN SECURITIES - 101.0%
(Cost $223,734,774,768)		223,734,774,768
NET OTHER ASSETS (LIABILITIES) - (1.0)%		(2,224,980,319)
NET ASSETS - 100%		$221,509,794,449

Security Type Abbreviations

VRDN – VARIABLE RATE DEMAND NOTE (A debt instrument that is payable upon demand, either daily, weekly or monthly)

Legend

(a) Yield represents either the annualized yield at the date of purchase, or the stated coupon rate, or, for floating and adjustable rate securities, the rate at period end.

(b) Coupon rates for floating and adjustable rate securities reflect the rates in effect at period end.

(d) Coupon is indexed to a floating interest rate which may be multiplied by a specified factor and/or subject to caps or floors.

(e) Represents a forward settling transaction and therefore no collateral securities had been allocated as of period end. The agreement contemplated the delivery of U.S. Treasury Obligations as collateral on settlement date.

Investment Valuation

Other Information

# Additional information on each counterparty to the repurchase agreement is as follows:

Repurchase Agreement / Counterparty	Value
$20,274,463,000 due 5/03/21 at 0.01%
BNY Mellon Capital Markets LLC	$1,244,316,000
Bank Of America, N.A.	1,195,232,000
Bank of America Securities, Inc.	1,483,032,000
Citibank N.A.	332,054,000
Citigroup Global Markets, Inc.	498,080,000
Credit Agricole CIB New York Branch	1,598,571,000
HSBC Securities (USA), Inc.	116,219,000
ING Financial Markets LLC	92,890,000
Mitsubishi UFJ Securities Holdings Ltd.	846,525,000
Mizuho Securities USA, Inc.	83,013,000
Nomura Securities International	2,265,429,000
RBC Dominion Securities, Inc.	2,964,529,000
Societe Generale (PARIS)	641,687,000
Sumitomo Mitsu Banking Corp. NY	4,202,837,000
Sumitomo Mitsui Banking Corp.	2,623,223,000
Wells Fargo Securities LLC	86,826,000
	$20,274,463,000
$47,783,000 due 5/03/21 at 0.01%
Wells Fargo Securities LLC	47,783,000
	$47,783,000

See accompanying notes which are an integral part of the financial statements.

Financial Statements

Statement of Assets and Liabilities

		April 30, 2021
Assets
Investment in securities, at value (including repurchase agreements of $83,175,246,000) — See accompanying schedule: Unaffiliated issuers (cost $223,734,774,768)		$223,734,774,768
Receivable for investments sold		129,261,401
Receivable for fund shares sold		1,125,568,366
Interest receivable		92,834,830
Prepaid expenses		68,936
Receivable from investment adviser for expense reductions		401,102
Other receivables		1,116,659
Total assets		225,084,026,062
Liabilities
Payable to custodian bank	$63,339
Payable for investments purchased	2,629,356,772
Payable for fund shares redeemed	929,804,087
Distributions payable	186,484
Accrued management fee	10,730,633
Other affiliated payables	432,562
Other payables and accrued expenses	3,657,736
Total liabilities		3,574,231,613
Net Assets		$221,509,794,449
Net Assets consist of:
Paid in capital		$221,509,640,282
Total accumulated earnings (loss)		154,167
Net Assets		$221,509,794,449
Net Asset Value and Maximum Offering Price
Capital Reserves Class:
Net Asset Value, offering price and redemption price per share ($7,539,252,314 ÷ 7,537,080,107 shares)		$1.00
Daily Money Class:
Net Asset Value, offering price and redemption price per share ($7,356,205,656 ÷ 7,354,285,207 shares)		$1.00
Advisor M Class:
Net Asset Value, offering price and redemption price per share ($124,205,328 ÷ 124,207,931 shares)		$1.00
Fidelity Government Money Market Fund:
Net Asset Value, offering price and redemption price per share ($200,115,905,422 ÷ 200,111,622,135 shares)		$1.00
Premium Class:
Net Asset Value, offering price and redemption price per share ($4,713,643,499 ÷ 4,712,462,786 shares)		$1.00
Class K6:
Net Asset Value, offering price and redemption price per share ($1,660,582,230 ÷ 1,660,603,231 shares)		$1.00

See accompanying notes which are an integral part of the financial statements.

Statement of Operations

		Year ended April 30, 2021
Investment Income
Interest		$327,721,531
Expenses
Management fee	$520,527,175
Transfer agent fees	335,825,450
Distribution and service plan fees	58,795,272
Accounting fees and expenses	4,915,007
Custodian fees and expenses	1,543,413
Independent trustees' fees and expenses	623,472
Registration fees	10,400,003
Audit	48,745
Legal	247,479
Miscellaneous	518,469
Total expenses before reductions	933,444,485
Expense reductions	(626,607,431)
Total expenses after reductions		306,837,054
Net investment income (loss)		20,884,477
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		229,324
Total net realized gain (loss)		229,324
Net increase in net assets resulting from operations		$21,113,801

See accompanying notes which are an integral part of the financial statements.

Statement of Changes in Net Assets

	Year ended April 30, 2021	Year ended April 30, 2020
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$20,884,477	$1,894,583,334
Net realized gain (loss)	229,324	1,249,552
Net increase in net assets resulting from operations	21,113,801	1,895,832,886
Distributions to shareholders	(20,874,874)	(1,894,622,301)
Share transactions - net increase (decrease)	33,214,705,842	66,219,398,590
Total increase (decrease) in net assets	33,214,944,769	66,220,609,175
Net Assets
Beginning of period	188,294,849,680	122,074,240,505
End of period	$221,509,794,449	$188,294,849,680

See accompanying notes which are an integral part of the financial statements.

Financial Highlights

Fidelity Government Money Market Fund Capital Reserves Class

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.009	.012	.003	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.009	.012	.003	–^A
Distributions from net investment income	–^A	(.009)	(.012)	(.003)	–^A
Total distributions	–^A	(.009)	(.012)	(.003)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.01%	.94%	1.26%	.27%	.01%
Ratios to Average Net Assets^C
Expenses before reductions	.96%	.97%	.96%	.96%	.97%
Expenses net of fee waivers, if any	.15%	.89%	.95%	.93%	.53%
Expenses net of all reductions	.15%	.89%	.95%	.93%	.53%
Net investment income (loss)	.01%	.87%	1.26%	.26%	.02%
Supplemental Data
Net assets, end of period (000 omitted)	$7,539,252	$7,470,316	$6,491,629	$8,466,153	$10,328,334

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

See accompanying notes which are an integral part of the financial statements.

Fidelity Government Money Market Fund Daily Money Class

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.012	.015	.005	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.012	.015	.005	–^A
Distributions from net investment income	–^A	(.012)	(.015)	(.005)	–^A
Total distributions	–^A	(.012)	(.015)	(.005)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.01%	1.16%	1.51%	.50%	.02%
Ratios to Average Net Assets^C
Expenses before reductions	.71%	.72%	.71%	.71%	.72%
Expenses net of fee waivers, if any	.15%	.67%	.70%	.70%	.52%
Expenses net of all reductions	.15%	.67%	.70%	.70%	.52%
Net investment income (loss)	.01%	1.08%	1.51%	.49%	.03%
Supplemental Data
Net assets, end of period (000 omitted)	$7,356,206	$7,835,091	$6,038,320	$6,913,180	$8,145,306

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

See accompanying notes which are an integral part of the financial statements.

Fidelity Government Money Market Fund Advisor M Class

Years ended April 30,	2021	2020	2019	2018 ^A
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^B	.012	.015	.005
Net realized and unrealized gain (loss)^B	–	–	–	–
Total from investment operations	–^B	.012	.015	.005
Distributions from net investment income	–^B	(.012)	(.015)	(.005)
Total distributions	–^B	(.012)	(.015)	(.005)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.01%	1.17%	1.52%	.48%
Ratios to Average Net Assets^E
Expenses before reductions	.71%	.72%	.71%	.72%^F
Expenses net of fee waivers, if any	.15%	.65%	.70%	.70%^F
Expenses net of all reductions	.15%	.64%	.69%	.69%^F
Net investment income (loss)	.01%	1.12%	1.53%	.71%^F
Supplemental Data
Net assets, end of period (000 omitted)	$124,205	$126,269	$50,630	$29,889

^A For the period July 6, 2017 (commencement of sale of shares) to April 30, 2018.

^B Amount represents less than $.0005 per share.

^C Total returns for periods of less than one year are not annualized.

^D Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^E Expense ratios reflect operating expenses of the class. Expenses before reductions do not reflect amounts reimbursed, waived, or reduced through arrangements with the investment adviser, brokerage services, or other offset arrangements, if applicable, and do not represent the amount paid by the class during periods when reimbursements, waivers or reductions occur.

^F Annualized

See accompanying notes which are an integral part of the financial statements.

Fidelity Government Money Market Fund

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.014	.018	.008	.001
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.014	.018	.008	.001
Distributions from net investment income	–^A	(.014)	(.018)	(.008)	(.001)
Total distributions	–^A	(.014)	(.018)	(.008)	(.001)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.01%	1.42%	1.79%	.78%	.12%
Ratios to Average Net Assets^C
Expenses before reductions	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.15%	.42%	.42%	.42%	.42%
Expenses net of all reductions	.15%	.42%	.42%	.42%	.42%
Net investment income (loss)	.01%	1.33%	1.79%	.81%	.14%
Supplemental Data
Net assets, end of period (000 omitted)	$200,115,905	$165,823,962	$104,973,598	$86,131,220	$63,580,065

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

See accompanying notes which are an integral part of the financial statements.

Fidelity Government Money Market Fund Premium Class

Years ended April 30,	2021	2020	2019	2018	2017
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	.015	.019	.009	.002
Net realized and unrealized gain (loss)^A	–	–	–	–	–
Total from investment operations	–^A	.015	.019	.009	.002
Distributions from net investment income	–^A	(.015)	(.019)	(.009)	(.002)
Total distributions	–^A	(.015)	(.019)	(.009)	(.002)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B	.01%	1.52%	1.90%	.89%	.22%
Ratios to Average Net Assets^C
Expenses before reductions	.36%	.37%	.36%	.36%	.37%
Expenses net of fee waivers, if any	.15%	.32%	.32%	.32%	.32%
Expenses net of all reductions	.15%	.32%	.32%	.32%	.32%
Net investment income (loss)	- %^D	1.43%	1.89%	.89%	.24%
Supplemental Data
Net assets, end of period (000 omitted)	$4,713,643	$5,726,124	$4,115,468	$2,901,645	$2,444,687

^A Amount represents less than $.0005 per share.

^B Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^D Amount represents less than .005%.

See accompanying notes which are an integral part of the financial statements.

Fidelity Government Money Market Fund Class K6

Years ended April 30,	2021	2020	2019	2018 ^A
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	–^B	.016	.019	.003
Net realized and unrealized gain (loss)^B	–	–	–	–
Total from investment operations	–^B	.016	.019	.003
Distributions from net investment income	–^B	(.016)	(.019)	(.003)
Total distributions	–^B	(.016)	(.019)	(.003)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.01%	1.59%	1.97%	.34%
Ratios to Average Net Assets^E
Expenses before reductions	.27%	.28%	.27%	.27%^F
Expenses net of fee waivers, if any	.14%	.25%	.25%	.25%^F
Expenses net of all reductions	.14%	.25%	.25%	.25%^F
Net investment income (loss)	.01%	1.50%	1.96%	1.47%^F
Supplemental Data
Net assets, end of period (000 omitted)	$1,660,582	$1,313,087	$404,595	$46,354

^A For the period January 24, 2018 (commencement of sale of shares) to April 30, 2018.

^B Amount represents less than $.0005 per share.

^C Total returns for periods of less than one year are not annualized.

^D Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^F Annualized

See accompanying notes which are an integral part of the financial statements.

Notes to Financial Statements

For the period ended April 30, 2021

1. Organization.

Fidelity Government Money Market Fund (the Fund) is a fund of Fidelity Hereford Street Trust (the Trust) and is authorized to issue an unlimited number of shares. The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Delaware statutory trust. The Fund offers Capital Reserves Class, Daily Money Class, Advisor M Class, Fidelity Government Money Market Fund, Premium Class and Class K6 shares, each of which has equal rights as to assets and voting privileges. Each class has exclusive voting rights with respect to matters that affect that class.

2. Significant Accounting Policies.

Investment Valuation. The Fund categorizes the inputs to valuation techniques used to value its investments into a disclosure hierarchy consisting of three levels as shown below:

Level 1 – quoted prices in active markets for identical investments
Level 2 – other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, etc.)
Level 3 – unobservable inputs (including the Fund's own assumptions based on the best information available)

Class Allocations and Expenses. Investment income, realized and unrealized capital gains and losses, common expenses of a fund, and certain fund-level expense reductions, if any, are allocated daily on a pro-rata basis to each class based on the relative net assets of each class to the total net assets of a fund. Each class differs with respect to transfer agent and distribution and service plan fees incurred, as applicable. Certain expense reductions may also differ by class, if applicable. For the reporting period, the allocated portion of income and expenses to each class as a percent of its average net assets may vary due to the timing of recording these transactions in relation to fluctuating net assets of the classes. Expenses directly attributable to a fund are charged to that fund. Expenses attributable to more than one fund are allocated among the respective funds on the basis of relative net assets or other appropriate methods. Expenses included in the accompanying financial statements reflect the expenses of that fund and do not include any expenses associated with any underlying mutual funds or exchange-traded funds. Although not included in a fund's expenses, a fund indirectly bears its proportionate share of these expenses through the net asset value of each underlying mutual fund or exchange-traded fund. Expense estimates are accrued in the period to which they relate and adjustments are made when actual amounts are known.

Fidelity Government Money Market Fund

$1,116,659

Distributions are declared and recorded daily and paid monthly from net investment income. Distributions from realized gains, if any, are declared and recorded on the ex-dividend date. Income and capital gain distributions are declared separately for each class. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from GAAP. In addition, the Fund claimed a portion of the payment made to redeeming shareholders as a distribution for income tax purposes.

Book-tax differences are primarily due to deferred trustees compensation and losses deferred due to wash sales.

As of period end, the cost and unrealized appreciation (depreciation) in securities for federal income tax purposes were as follows:

Gross unrealized appreciation	$–
Gross unrealized depreciation	–
Net unrealized appreciation (depreciation)	$–
Tax Cost	$223,734,774,768

The tax-based components of distributable earnings as of period end were as follows:

Undistributed ordinary income

$154,427

The tax character of distributions paid was as follows:

	April 30, 2021	April 30, 2020
Ordinary Income	$20,874,874	$ 1,894,622,301

Repurchase Agreements. Pursuant to an Exemptive Order issued by the Securities and Exchange Commission, funds and other registered investment companies having management contracts with Fidelity Management and Research Company LLC, or its affiliates are permitted to transfer uninvested cash balances into joint trading accounts which are then invested in repurchase agreements. Funds may also invest directly with institutions in repurchase agreements. Repurchase agreements may be collateralized by cash or government securities. Upon settlement date, collateral is held in segregated accounts with custodian banks and may be obtained in the event of a default of the counterparty. The collateral balance is monitored on a daily basis to ensure it is at least equal to the principal amount of the repurchase agreement (including accrued interest). In the event of a default by the counterparty, realization of the collateral proceeds could be delayed, during which time the value of the collateral may decline.

3. Fees and Other Transactions with Affiliates.

Management Fee and Expense Contract. Fidelity Management & Research Company LLC (the investment adviser) and its affiliates provide the Fund with investment management related services for which the Fund pays a monthly management fee that is based on an annual rate of .25% of the Fund's average net assets. Under the expense contract, total expenses of Fidelity Government Money Market Fund are limited to an annual rate of .42% of the class' average net assets, with certain exceptions.

During the period, the investment adviser or its affiliates waived a portion of these fees.

Distribution and Service Plan Fees. In accordance with Rule 12b-1 of the 1940 Act, the Fund has adopted separate Distribution and Service Plans for each class of shares. Certain classes pay Fidelity Distributors Company LLC (FDC), an affiliate of the investment adviser, separate Distribution and Service Fees, each of which is based on an annual percentage of each class' average net assets. In addition, FDC may pay financial intermediaries for selling shares of the Fund and providing shareholder support services. For the period, the Distribution and Service Fee rates, total fees and amounts retained by FDC were as follows:

	Distribution Fee	Service Fee	Total Fees	Retained by FDC
Capital Reserves Class	.25%	.25%	$39,432,206	$36,265,900
Daily Money Class	-%	.25%	19,044,754	17,478,914
Advisor M Class	-%	.25%	318,312	291,999
			$58,795,272	$54,036,813

During the period, the investment adviser or its affiliates waived a portion of these fees.

Sales Load. FDC receives the proceeds of contingent deferred sales charges for Daily Money Class shares purchased by exchange from Class A or Class M shares of a Fidelity fund that were subject to these charges. In addition, FDC receives deferred sales charges for Advisor M Class shares purchased by exchange from Class M shares of a Fidelity fund that were subject to these charges.

For the period, sales charge amounts retained by FDC were as follows:

	Retained by FDC
Daily Money Class	$8,259
Advisor M Class	$1,196

Transfer Agent Fees. Fidelity Investments Institutional Operations Company LLC (FIIOC), an affiliate of the investment adviser, is the transfer, dividend disbursing and shareholder servicing agent for each class of the Fund. FIIOC receives asset-based fees with respect to each account. FIIOC pays for typesetting, printing and mailing of shareholder reports, except proxy statements. Each class pays a transfer agent fee equal to an annual rate of .20% of class-level average net assets, with the exception of Premium Class and Class K6 which pays .10% and .01% of class-level average net assets, respectively.

Under the expense contract, Fidelity Government Money Market Fund will pay a portion of the transfer agent fee at an annual rate of up to .17% of class-level average net assets.

For the period, transfer agent fees for each class were as follows:

	Amount	% of Class-Level Average Net Assets
Capital Reserves Class	$15,772,882	.20
Daily Money Class	15,236,410	.20
Advisor M Class	254,720	.20
Fidelity Government Money Market Fund	299,020,898	.16
Premium Class	5,382,472	.10
Class K6	158,068	.01
	$335,825,450

During the period, the investment adviser or its affiliates waived a portion of these fees.

	% of Average Net Assets
Fidelity Government Money Market Fund	–%^(a)

(a) Amount represents less than .005%.

	Purchases ($)	Sales ($)
Fidelity Government Money Market Fund	74,100,000	–

4. Expense Reductions.

The investment adviser contractually agreed to reimburse expenses of each class to the extent annual operating expenses exceeded certain levels of class-level average net assets as noted in the table below. This reimbursement will remain in place through August 31, 2022. Some expenses, for example the compensation of the independent Trustees and certain other expenses such as interest expense, are excluded from this reimbursement.

The following classes were in reimbursement during the period:

	Expense Limitations	Reimbursement
Capital Reserves Class	.95%	$707,616
Daily Money Class	.70%	671,010
Advisor M Class	.70%	11,449
Premium Class	.32%	2,077,645
Class K6	.25%	295,351
		$3,763,071

Capital Reserves Class	$63,097,939
Daily Money Class	41,751,124
Advisor M Class	699,987
Fidelity Government Money Market Fund	506,578,115
Premium Class	8,970,707
Class K6	1,694,361

	Expense reduction
Fidelity Government Money Market Fund	24

In addition, during the period the investment adviser or an affiliate reimbursed and/or waived a portion of fund-level operating expenses in the amount of $129.

5. Distributions to Shareholders.

Distributions to shareholders of each class were as follows:

	Year ended April 30, 2021	Year ended April 30, 2020
Fidelity Government Money Market Fund
Distributions to shareholders
Capital Reserves Class	$786,905	$60,356,967
Daily Money Class	760,813	76,178,608
Advisor M Class	12,529	679,470
Fidelity Government Money Market Fund	18,527,218	1,678,425,378
Premium Class	574,686	68,936,329
Class K6	212,723	10,045,549
Total	$20,874,874	$1,894,622,301

6. Share Transactions.

Share transactions for each class of shares at a $1.00 per share were as follows and may contain automatic conversions between classes or exchanges between affiliated funds:

	Shares	Shares	Dollars	Dollars
	Year ended April 30, 2021	Year ended April 30, 2020	Year ended April 30, 2021	Year ended April 30, 2020
Fidelity Government Money Market Fund
Capital Reserves Class
Shares sold	32,661,536,522	31,933,001,084	$32,661,536,522	$31,933,001,084
Reinvestment of distributions	499,618	37,539,053	499,618	37,539,053
Shares redeemed	(32,593,112,615)	(30,992,019,053)	(32,593,112,615)	(30,992,019,053)
Net increase (decrease)	68,923,525	978,521,084	$68,923,525	$978,521,084
Daily Money Class
Shares sold	24,900,123,722	28,776,861,260	$24,900,123,722	$28,776,861,260
Reinvestment of distributions	542,620	53,974,169	542,620	53,974,169
Shares redeemed	(25,379,435,893)	(27,034,456,625)	(25,379,435,893)	(27,034,456,625)
Net increase (decrease)	(478,769,551)	1,796,378,804	$(478,769,551)	$1,796,378,804
Advisor M Class
Shares sold	168,543,544	185,769,558	$168,543,544	$185,769,558
Reinvestment of distributions	12,309	655,877	12,309	655,877
Shares redeemed	(170,619,521)	(110,783,720)	(170,619,521)	(110,783,720)
Net increase (decrease)	(2,063,668)	75,641,715	$(2,063,668)	$75,641,715
Fidelity Government Money Market Fund
Shares sold	704,541,729,477	541,543,937,250	$704,541,729,477	$541,543,937,250
Reinvestment of distributions	17,041,021	1,535,792,307	17,041,021	1,535,792,307
Shares redeemed	(670,267,422,261)	(482,229,701,607)	(670,267,422,261)	(482,229,701,607)
Net increase (decrease)	34,291,348,237	60,850,027,950	$34,291,348,237	$60,850,027,950
Premium Class
Shares sold	2,950,419,613	5,782,487,798	$2,950,419,613	$5,782,487,798
Reinvestment of distributions	545,983	64,936,594	545,983	64,936,594
Shares redeemed	(3,963,201,241)	(4,237,106,538)	(3,963,201,241)	(4,237,106,538)
Net increase (decrease)	(1,012,235,645)	1,610,317,854	$(1,012,235,645)	$1,610,317,854
Class K6
Shares sold	1,666,993,981	1,582,341,872	$1,666,993,981	$1,582,341,872
Reinvestment of distributions	212,723	10,037,137	212,723	10,037,137
Shares redeemed	(1,319,703,760)	(683,867,826)	(1,319,703,760)	(683,867,826)
Net increase (decrease)	347,502,944	908,511,183	$347,502,944	$908,511,183

7. Other.

8. Coronavirus (COVID-19) Pandemic.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Fidelity Hereford Street Trust and Shareholders of Fidelity Government Money Market Fund

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities, including the schedule of investments, of Fidelity Government Money Market Fund (one of the funds constituting Fidelity Hereford Street Trust, referred to hereafter as the “Fund”) as of April 30, 2021, the related statement of operations for the year ended April 30, 2021, the statement of changes in net assets for each of the two years in the period ended April 30, 2021, including the related notes, and the financial highlights for each of the periods indicated therein (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period ended April 30, 2021 and the financial highlights for each of the periods indicated therein in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of April 30, 2021 by correspondence with the custodians and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

June 14, 2021

We have served as the auditor of one or more investment companies in the Fidelity group of funds since 1932.

Trustees and Officers

The fund’s Statement of Additional Information (SAI) includes more information about the Trustees. To request a free copy, call Fidelity at 1-800-544-8544 if you’re an individual investing directly with Fidelity, call 1-800-835-5092 if you’re a plan sponsor or participant with Fidelity as your recordkeeper or call 1-877-208-0098 on institutional accounts or if you’re an advisor or invest through one.

Interested Trustees*:

Correspondence intended for a Trustee who is an interested person may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Abigail P. Johnson (1961)

Year of Election or Appointment: 2009

Trustee

Chairman of the Board of Trustees

Jennifer Toolin McAuliffe (1959)

Year of Election or Appointment: 2016

Trustee

* Determined to be an “Interested Trustee” by virtue of, among other things, his or her affiliation with the trust or various entities under common control with FMR.

Independent Trustees:

Correspondence intended for an Independent Trustee may be sent to Fidelity Investments, P.O. Box 55235, Boston, Massachusetts 02205-5235.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Elizabeth S. Acton (1951)

Year of Election or Appointment: 2013

Trustee

Ann E. Dunwoody (1953)

Year of Election or Appointment: 2018

Trustee

John Engler (1948)

Year of Election or Appointment: 2014

Trustee

Robert F. Gartland (1951)

Year of Election or Appointment: 2010

Trustee

Arthur E. Johnson (1947)

Year of Election or Appointment: 2008

Trustee

Chairman of the Independent Trustees

Michael E. Kenneally (1954)

Year of Election or Appointment: 2009

Trustee

Vice Chairman of the Independent Trustees

Marie L. Knowles (1946)

Year of Election or Appointment: 2001

Trustee

Mark A. Murray (1954)

Year of Election or Appointment: 2016

Trustee

Advisory Board Members and Officers:

Correspondence intended for an officer may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210. Officers appear below in alphabetical order.

Name, Year of Birth; Principal Occupation

Robert W. Helm (1957)

Year of Election or Appointment: 2021

Member of the Advisory Board

Craig S. Brown (1977)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Brown also serves as Assistant Treasurer of other funds. Mr. Brown is an employee of Fidelity Investments (2013-present).

John J. Burke III (1964)

Year of Election or Appointment: 2018

Chief Financial Officer

David J. Carter (1973)

Year of Election or Appointment: 2020

Assistant Secretary

Mr. Carter also serves as Assistant Secretary of other funds. Mr. Carter serves as Vice President, Associate General Counsel (2010-present) and is an employee of Fidelity Investments (2005-present).

Jonathan Davis (1968)

Year of Election or Appointment: 2010

Assistant Treasurer

Laura M. Del Prato (1964)

Year of Election or Appointment: 2018

President and Treasurer

Colm A. Hogan (1973)

Year of Election or Appointment: 2016

Assistant Treasurer

Cynthia Lo Bessette (1969)

Year of Election or Appointment: 2019

Secretary and Chief Legal Officer (CLO)

Chris Maher (1972)

Year of Election or Appointment: 2013

Assistant Treasurer

Jamie Pagliocco (1964)

Year of Election or Appointment: 2020

Vice President

Kenneth B. Robins (1969)

Year of Election or Appointment: 2020

Chief Compliance Officer

Brett Segaloff (1972)

Year of Election or Appointment: 2021

Anti-Money Laundering (AML) Officer

Stacie M. Smith (1974)

Year of Election or Appointment: 2013

Assistant Treasurer

Marc L. Spector (1972)

Year of Election or Appointment: 2016

Deputy Treasurer

Jim Wegmann (1979)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Wegmann also serves as Assistant Treasurer of other funds. Mr. Wegmann is an employee of Fidelity Investments (2011-present).

Shareholder Expense Example

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (November 1, 2020 to April 30, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value November 1, 2020	Ending Account Value April 30, 2021	Expenses Paid During Period-^B November 1, 2020 to April 30, 2021
Fidelity Government Money Market Fund
Capital Reserves Class	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**
Daily Money Class	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**
Advisor M Class	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**
Fidelity Government Money Market Fund	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**
Premium Class	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**
Class K6	.10%
Actual		$1,000.00	$1,000.00	$.50**
Hypothetical-^C		$1,000.00	$1,024.30	$.50**

^A Annualized expense ratio reflects expenses net of applicable fee waivers.

^C 5% return per year before expenses

	Annualized Expense Ratio-^(a)	Expenses Paid
Fidelity Government Money Market Fund
Capital Reserves Class	.95%
Actual		$4.70
Hypothetical-^(b)		$4.76
Daily Money Class	.70%
Actual		$3.47
Hypothetical-^(b)		$3.51
Advisor M Class	.70%
Actual		$3.47
Hypothetical-^(b)		$3.51
Fidelity Government Money Market Fund	.42%
Actual		$2.08
Hypothetical-^(b)		$2.11
Premium Class	.32%
Actual		$1.59
Hypothetical-^(b)		$1.61
Class K6	.25%
Actual		$1.24
Hypothetical-^(b)		$1.25

(a) Annualized expense ratio reflects expenses net of applicable fee waivers.

(b) 5% return per year before expenses

Distributions (Unaudited)

The fund hereby designates as a capital gain dividend with respect to the taxable year ended April 30, 2021, $168,918, or, if subsequently determined to be different, the net capital gain of such year.

A total of 67.77% of the dividends distributed during the fiscal year was derived from interest on U.S. Government securities which is generally exempt from state income tax.

The fund designates $329,507,486 of distributions paid in the calendar year 2020 as qualifying to be taxed as interest-related dividends for nonresident alien shareholders.

The fund designates $397,792,316 of distributions paid in the calendar year 2020 as qualifying to be taxed as section 163(j) interest dividends.

The fund will notify shareholders in January 2022 of amounts for use in preparing 2021 income tax returns.

Fidelity Investments

SPU-ANN-0621
1.703529.123

Fidelity Flex® Funds

Fidelity Flex® Government Money Market Fund

Annual Report

April 30, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Report of Independent Registered Public Accounting Firm
Trustees and Officers
Shareholder Expense Example
Distributions

You may also call 1-800-544-3455 (for managed account clients) or 1-800-835-5092 (for retirement plan participants) to request a free copy of the proxy voting guidelines.

Standard & Poor's, S&P and S&P 500 are registered service marks of The McGraw-Hill Companies, Inc. and have been licensed for use by Fidelity Distributors Corporation.

Other third-party marks appearing herein are the property of their respective owners.

NOT FDIC INSURED •MAY LOSE VALUE •NO BANK GUARANTEE

Neither the Fund nor Fidelity Distributors Corporation is a bank.

Note to Shareholders:

Investment Summary/Performance (Unaudited)

Effective Maturity Diversification as of April 30, 2021

Days	% of fund's investments 4/30/21
1 - 7	41.1
8 - 30	14.7
31 - 60	13.6
61 - 90	9.9
91 - 180	18.2
> 180	2.5

Effective maturity is determined in accordance with the requirements of Rule 2a-7 under the Investment Company Act of 1940.

Asset Allocation (% of fund's net assets)

As of April 30, 2021 ^*
	U.S. Treasury Debt	29.6%
	U.S. Government Agency Debt	41.7%
	Repurchase Agreements	25.4%
	Net Other Assets (Liabilities)	3.3%

* Foreign investments - 13.2%

Effective maturity is determined in accordance with the requirements of Rule 2a-7 under the Investment Company Act of 1940.

Current 7-Day Yields

	4/30/21
Fidelity Flex® Government Money Market Fund	0.06%

Schedule of Investments April 30, 2021

Showing Percentage of Net Assets

U.S. Treasury Debt - 29.6%
	Yield(a)	Principal Amount	Value
U.S. Treasury Obligations - 29.6%
U.S. Treasury Bills
5/6/21 to 12/2/21	0.01 to 0.13%	$24,950,000	$24,946,949
U.S. Treasury Notes
7/31/21 to 7/31/22	0.03 to 0.32 (b)	4,300,000	4,314,349
TOTAL U.S. TREASURY DEBT
(Cost $29,261,298)			29,261,298

U.S. Government Agency Debt - 41.7%
Federal Agencies - 41.7%
Fannie Mae
5/6/21 to 7/29/22	0.04 to 0.24 (b)	4,116,000	4,122,184
Federal Farm Credit Bank
5/26/21 to 3/8/22	0.03 to 0.17 (b)	4,075,000	4,087,180
Federal Home Loan Bank
5/3/21 to 12/15/22	0.02 to 0.25 (b)	31,440,000	31,463,296
Freddie Mac
8/12/21 to 8/18/22	0.10 to 0.17 (b)	1,625,000	1,628,845
TOTAL U.S. GOVERNMENT AGENCY DEBT
(Cost $41,301,505)			41,301,505

U.S. Government Agency Repurchase Agreement - 10.3%
	Maturity Amount	Value
In a joint trading account at 0.01% dated 4/30/21 due 5/3/21 (Collateralized by (U.S. Government Obligations) #	$677,001	$677,000
With:
ABN AMRO Bank NV at 0.02%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,027,617, 0.38% - 5.50%, 8/15/24 - 8/15/45)	1,000,002	1,000,000
Barclays Bank PLC at 0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Government Obligations valued at $1,020,002, 2.00%, 4/1/51)	1,000,002	1,000,000
4/27/21 due 5/4/21 (Collateralized by U.S. Government Obligations valued at $1,020,002, 2.00%, 4/1/51)	1,000,002	1,000,000
4/28/21 due 5/5/21 (Collateralized by U.S. Government Obligations valued at $1,020,002, 2.00%, 4/1/51)	1,000,002	1,000,000
BMO Harris Bank NA at:
0.05%, dated 4/12/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $1,020,030, 1.50% - 3.00%, 4/1/36 - 4/20/51)	1,000,126	1,000,000
0.07%, dated 2/5/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $510,086, 2.75% - 3.00%, 8/31/25 - 4/20/51)	500,088	500,000
Citibank NA at:
0.01%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,139, 0.25% - 5.00%, 2/28/22 - 8/15/44)	1,000,002	1,000,000
0.02%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,053, 0.13% - 0.63%, 4/30/23 - 5/15/30)	1,000,004	1,000,000
Citigroup Global Capital Markets, Inc. at 0.02%, dated 4/27/21 due 5/4/21 (Collateralized by U.S. Government Obligations valued at $1,020,500, 2.50% - 4.50%, 9/1/49)	1,000,004	1,000,000
RBC Financial Group at 0.03%, dated 3/23/21 due 5/7/21 (Collateralized by U.S. Government Obligations valued at $1,020,425, 2.00% - 4.00%, 8/1/33 - 10/1/50)	1,000,077	1,000,000
TOTAL U.S. GOVERNMENT AGENCY REPURCHASE AGREEMENT
(Cost $10,177,000)		10,177,000

U.S. Treasury Repurchase Agreement - 15.1%
With:
BNP Paribas, SA at 0.02%, dated 4/12/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,048, 0.00% - 1.38%, 8/12/21 - 11/15/40)	1,000,012	1,000,000
Commerz Markets LLC at 0.01%, dated:
4/27/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,022,113, 2.00% - 2.88%, 5/15/28 - 2/15/50)	1,000,002	1,000,000
4/28/21 due 5/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,106, 0.63% - 2.88%, 5/15/28 - 5/15/30)	1,000,002	1,000,000
Credit AG at:
0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,017, 2.75%, 6/30/25)	1,000,002	1,000,000
4/28/21 due 5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,017, 2.75%, 6/30/25)	1,000,002	1,000,000
5/3/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations)(c)	1,000,001	1,000,000
0.02%, dated 4/28/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,017, 2.75%, 6/30/25)	1,000,016	1,000,000
ING Financial Markets LLC at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,029,871, 1.38%, 6/30/23)	1,000,001	1,000,000
J.P. Morgan Securities, LLC at 0.01%, dated:
4/26/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,002, 0.13% - 7.63%, 3/15/22 - 1/31/26)	1,000,002	1,000,000
4/30/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,001, 0.13% - 8.00%, 11/15/21 - 1/31/26)	1,000,002	1,000,000
Mizuho Bank, Ltd. at 0.01%, dated 4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,022,523, 2.38%, 5/15/29)	1,000,001	1,000,000
MUFG Securities EMEA PLC at 0.01%, dated:
4/27/21 due:
5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,021,809, 2.00% - 3.13%, 10/31/22 - 5/15/48)	1,000,002	1,000,000
5/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,025,918, 1.50% - 3.13%, 2/15/30 - 5/15/48)	1,000,002	1,000,000
4/30/21 due 5/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,019,717, 0.63%, 11/30/27)	1,000,001	1,000,000
5/3/21 due 5/7/21 (Collateralized by U.S. Treasury Obligations)(c)	1,000,002	1,000,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $15,000,000)		15,000,000
TOTAL INVESTMENT IN SECURITIES - 96.7%
(Cost $95,739,803)		95,739,803
NET OTHER ASSETS (LIABILITIES) - 3.3%		3,239,606
NET ASSETS - 100%		$98,979,409

Legend

(a) Yield represents either the annualized yield at the date of purchase, or the stated coupon rate, or, for floating and adjustable rate securities, the rate at period end.

(b) Coupon rates for floating and adjustable rate securities reflect the rates in effect at period end.

(c) Represents a forward settling transaction and therefore no collateral securities had been allocated as of period end. The agreement contemplated the delivery of U.S. Treasury Obligations as collateral on settlement date.

Investment Valuation

Other Information

# Additional information on each counterparty to the repurchase agreement is as follows:

Repurchase Agreement / Counterparty	Value
$677,000 due 5/03/21 at 0.01%
BNY Mellon Capital Markets LLC	$181,000
Bank Of America, N.A.	486,000
Wells Fargo Securities LLC	10,000
	$677,000

See accompanying notes which are an integral part of the financial statements.

Financial Statements

Statement of Assets and Liabilities

		April 30, 2021
Assets
Investment in securities, at value (including repurchase agreements of $25,177,000) — See accompanying schedule: Unaffiliated issuers (cost $95,739,803)		$95,739,803
Cash		185
Receivable for fund shares sold		10,151,452
Interest receivable		78,632
Total assets		105,970,072
Liabilities
Payable for investments purchased	$4,907,689
Payable for fund shares redeemed	2,081,555
Distributions payable	1,419
Total liabilities		6,990,663
Net Assets		$98,979,409
Net Assets consist of:
Paid in capital		$98,978,679
Total accumulated earnings (loss)		730
Net Assets		$98,979,409
Net Asset Value, offering price and redemption price per share ($98,979,409 ÷ 98,977,277 shares)		$1.00

See accompanying notes which are an integral part of the financial statements.

Statement of Operations

		Year ended April 30, 2021
Investment Income
Interest		$103,995
Expenses
Independent trustees' fees and expenses	$212
Total expenses before reductions	212
Expense reductions	(15)
Total expenses after reductions		197
Net investment income (loss)		103,798
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		335
Total net realized gain (loss)		335
Net increase in net assets resulting from operations		$104,133

See accompanying notes which are an integral part of the financial statements.

Statement of Changes in Net Assets

	Year ended April 30, 2021	Year ended April 30, 2020
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$103,798	$609,225
Net realized gain (loss)	335	1,084
Net increase in net assets resulting from operations	104,133	610,309
Distributions to shareholders	(103,068)	(609,282)
Share transactions
Proceeds from sales of shares	3,017,435,302	1,066,466,133
Reinvestment of distributions	79,006	481,328
Cost of shares redeemed	(2,969,478,102)	(1,038,050,400)
Net increase (decrease) in net assets and shares resulting from share transactions	48,036,206	28,897,061
Total increase (decrease) in net assets	48,037,271	28,898,088
Net Assets
Beginning of period	50,942,138	22,044,050
End of period	$98,979,409	$50,942,138
Other Information
Shares
Sold	3,017,435,302	1,066,466,133
Issued in reinvestment of distributions	79,006	481,328
Redeemed	(2,969,478,102)	(1,038,050,400)
Net increase (decrease)	48,036,206	28,897,061

See accompanying notes which are an integral part of the financial statements.

Financial Highlights

Fidelity Flex Government Money Market Fund


Years ended April 30,	2021	2020	2019	2018	2017 ^A
Selected Per–Share Data
Net asset value, beginning of period	$1.00	$1.00	$1.00	$1.00	$1.00
Income from Investment Operations
Net investment income (loss)	.002	.018	.022	.012	.001
Net realized and unrealized gain (loss)	(.001)	–^B	–^B	–^B	–
Total from investment operations	.001	.018	.022	.012	.001
Distributions from net investment income	(.001)	(.018)	(.022)	(.012)	(.001)
Total distributions	(.001)	(.018)	(.022)	(.012)	(.001)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.15%	1.81%	2.22%	1.23%	.12%
Ratios to Average Net Assets^E
Expenses before reductions^F	-%	-%	-%	-%	- %^G
Expenses net of fee waivers, if any^F	-%	-%	-%	-%	- %^G
Expenses net of all reductions^F	-%	-%	-%	-%	- %^G
Net investment income (loss)	.14%	1.64%	2.14%	1.39%	.78%^G
Supplemental Data
Net assets, end of period (000 omitted)	$98,979	$50,942	$22,044	$53,685	$5,006

^A For the period March 8, 2017 (commencement of operations) to April 30, 2017.

^B Amount represents less than $.0005 per share.

^C Total returns for periods of less than one year are not annualized.

^D Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^E Expense ratios reflect operating expenses of the class. Expenses before reductions do not reflect amounts reimbursed, waived, or reduced through arrangements with the investment advisor, brokerage services, or other offset arrangements, if applicable, and do not represent the amount paid by the class during periods when reimbursements, waivers or reductions occur.

^F Amount represents less than .005%.

^G Annualized

See accompanying notes which are an integral part of the financial statements.

Notes to Financial Statements

For the period ended April 30, 2021

1. Organization.

Fidelity Flex Government Money Market Fund (the Fund) is a fund of Fidelity Hereford Street Trust (the Trust) and is authorized to issue an unlimited number of shares. Share transactions on the Statement of Changes in Net Assets may contain exchanges between affiliated funds. The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Delaware statutory trust. The Fund is available only to certain fee-based accounts and advisory programs offered by Fidelity.

2. Significant Accounting Policies.

Investment Valuation. The Fund categorizes the inputs to valuation techniques used to value its investments into a disclosure hierarchy consisting of three levels as shown below:

Level 1 – quoted prices in active markets for identical investments
Level 2 – other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, etc.)
Level 3 – unobservable inputs (including the Fund's own assumptions based on the best information available)

As of period end, the cost and unrealized appreciation (depreciation) in securities for federal income tax purposes were as follows:

Gross unrealized appreciation	$–
Gross unrealized depreciation	–
Net unrealized appreciation (depreciation)	$–
Tax Cost	$95,739,803

The tax-based components of distributable earnings as of period end were as follows:

Undistributed ordinary income

$729

The tax character of distributions paid was as follows:

	April 30, 2021	April 30, 2020
Ordinary Income	$103,068	$ 609,282

Repurchase Agreements. Pursuant to an Exemptive Order issued by the Securities and Exchange Commission, funds and other registered investment companies having management contracts with Fidelity Management and Research Company LLC, or its affiliates are permitted to transfer uninvested cash balances into joint trading accounts which are then invested in repurchase agreements. Funds may also invest directly with institutions in repurchase agreements. Repurchase agreements may be collateralized by cash or government securities. Upon settlement date, collateral is held in segregated accounts with custodian banks and may be obtained in the event of a default of the counterparty. The collateral balance is monitored on a daily basis to ensure it is at least equal to the principal amount of the repurchase agreement (including accrued interest). In the event of a default by the counterparty, realization of the collateral proceeds could be delayed, during which time the value of the collateral may decline.

3. Fees and Other Transactions with Affiliates.

Management Fee. Fidelity Management & Research Company LLC (the investment adviser) and its affiliates provide the Fund with investment management related services and the Fund does not pay any fees for these services. Under the management contract, the investment adviser or an affiliate pays all other expenses of the Fund, excluding fees and expenses of the independent Trustees, and certain miscellaneous expenses such as proxy and shareholder meeting expenses.

4. Expense Reductions.

Through arrangements with the Fund's custodian, credits realized as a result of certain uninvested cash balances were used to reduce the Fund's expenses by $15

5. Other.

6. Coronavirus (COVID-19) Pandemic.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Fidelity Hereford Street Trust and Shareholders of Fidelity Flex Government Money Market Fund

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities, including the schedule of investments, of Fidelity Flex Government Money Market Fund (one of the funds constituting Fidelity Hereford Street Trust, referred to hereafter as the “Fund”) as of April 30, 2021, the related statement of operations for the year ended April 30, 2021, the statement of changes in net assets for each of the two years in the period ended April 30, 2021, including the related notes, and the financial highlights for each of the four years in the period ended April 30, 2021 and for the period March 8, 2017 (commencement of operations) to April 30, 2017 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period ended April 30, 2021 and the financial highlights for each of the four years in the period ended April 30, 2021 and for the period March 8, 2017 (commencement of operations) to April 30, 2017 in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of April 30, 2021 by correspondence with the custodians and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

June 14, 2021

We have served as the auditor of one or more investment companies in the Fidelity group of funds since 1932.

Trustees and Officers

The fund’s Statement of Additional Information (SAI) includes more information about the Trustees. To request a free copy, call Fidelity at 1-800-544-3455 (for managed account clients) or 1-800-835-5092 (for retirement plan participants).

Interested Trustees*:

Correspondence intended for a Trustee who is an interested person may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Abigail P. Johnson (1961)

Year of Election or Appointment: 2009

Trustee

Chairman of the Board of Trustees

Jennifer Toolin McAuliffe (1959)

Year of Election or Appointment: 2016

Trustee

* Determined to be an “Interested Trustee” by virtue of, among other things, his or her affiliation with the trust or various entities under common control with FMR.

Independent Trustees:

Correspondence intended for an Independent Trustee may be sent to Fidelity Investments, P.O. Box 55235, Boston, Massachusetts 02205-5235.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Elizabeth S. Acton (1951)

Year of Election or Appointment: 2013

Trustee

Ann E. Dunwoody (1953)

Year of Election or Appointment: 2018

Trustee

John Engler (1948)

Year of Election or Appointment: 2014

Trustee

Robert F. Gartland (1951)

Year of Election or Appointment: 2010

Trustee

Arthur E. Johnson (1947)

Year of Election or Appointment: 2008

Trustee

Chairman of the Independent Trustees

Michael E. Kenneally (1954)

Year of Election or Appointment: 2009

Trustee

Vice Chairman of the Independent Trustees

Marie L. Knowles (1946)

Year of Election or Appointment: 2001

Trustee

Mark A. Murray (1954)

Year of Election or Appointment: 2016

Trustee

Advisory Board Members and Officers:

Correspondence intended for an officer may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210. Officers appear below in alphabetical order.

Name, Year of Birth; Principal Occupation

Robert W. Helm (1957)

Year of Election or Appointment: 2021

Member of the Advisory Board

Craig S. Brown (1977)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Brown also serves as Assistant Treasurer of other funds. Mr. Brown is an employee of Fidelity Investments (2013-present).

John J. Burke III (1964)

Year of Election or Appointment: 2018

Chief Financial Officer

David J. Carter (1973)

Year of Election or Appointment: 2020

Assistant Secretary

Mr. Carter also serves as Assistant Secretary of other funds. Mr. Carter serves as Vice President, Associate General Counsel (2010-present) and is an employee of Fidelity Investments (2005-present).

Jonathan Davis (1968)

Year of Election or Appointment: 2010

Assistant Treasurer

Laura M. Del Prato (1964)

Year of Election or Appointment: 2018

President and Treasurer

Colm A. Hogan (1973)

Year of Election or Appointment: 2016

Assistant Treasurer

Cynthia Lo Bessette (1969)

Year of Election or Appointment: 2019

Secretary and Chief Legal Officer (CLO)

Chris Maher (1972)

Year of Election or Appointment: 2013

Assistant Treasurer

Jamie Pagliocco (1964)

Year of Election or Appointment: 2020

Vice President

Kenneth B. Robins (1969)

Year of Election or Appointment: 2020

Chief Compliance Officer

Brett Segaloff (1972)

Year of Election or Appointment: 2021

Anti-Money Laundering (AML) Officer

Stacie M. Smith (1974)

Year of Election or Appointment: 2013

Assistant Treasurer

Marc L. Spector (1972)

Year of Election or Appointment: 2016

Deputy Treasurer

Jim Wegmann (1979)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Wegmann also serves as Assistant Treasurer of other funds. Mr. Wegmann is an employee of Fidelity Investments (2011-present).

Shareholder Expense Example

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (November 1, 2020 to April 30, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value November 1, 2020	Ending Account Value April 30, 2021	Expenses Paid During Period-^B November 1, 2020 to April 30, 2021
Fidelity Flex Government Money Market Fund	- %-^C
Actual		$1,000.00	$1,000.50	$--^D
Hypothetical-^E		$1,000.00	$1,024.79	$--^D

^A Annualized expense ratio reflects expenses net of applicable fee waivers.

^C Amount represents less than $.005.

^D Amount represents less than .005%.

^E 5% return per year before expenses

Distributions (Unaudited)

A total of 70.50% of the dividends distributed during the fiscal year was derived from interest on U.S. Government securities which is generally exempt from state income tax.

The fund designates $210,231 of distributions paid during the period January 1, 2021 to April 30, 2021 as qualifying to be taxed as interest-related dividends for nonresident alien shareholders.

The fund designates $251,865 of distributions paid in the calendar year 2020 as qualifying to be taxed as section 163(j) interest dividends.

The fund will notify shareholders in January 2022 of amounts for use in preparing 2021 income tax returns.

Fidelity Investments

ZGY-ANN-0621
1.9881599.104

Fidelity® Series Treasury Bill Index Fund

Annual Report

April 30, 2021

Contents

Note to Shareholders
Performance
Management's Discussion of Fund Performance
Investment Summary
Schedule of Investments
Financial Statements
Notes to Financial Statements
Report of Independent Registered Public Accounting Firm
Trustees and Officers
Shareholder Expense Example
Distributions
Liquidity Risk Management Program

You may also call 1-800-544-8544 to request a free copy of the proxy voting guidelines.

Standard & Poor's, S&P and S&P 500 are registered service marks of The McGraw-Hill Companies, Inc. and have been licensed for use by Fidelity Distributors Corporation.

Other third-party marks appearing herein are the property of their respective owners.

NOT FDIC INSURED •MAY LOSE VALUE •NO BANK GUARANTEE

Neither the Fund nor Fidelity Distributors Corporation is a bank.

Note to Shareholders:

Performance: The Bottom Line

Average annual total return reflects the change in the value of an investment, assuming reinvestment of distributions from dividend income and capital gains (the profits earned upon the sale of securities that have grown in value, if any) and assuming a constant rate of performance each year. The hypothetical investment and the average annual total returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. During periods of reimbursement by Fidelity, a fund’s total return will be greater than it would be had the reimbursement not occurred. How a fund did yesterday is no guarantee of how it will do tomorrow.

Average Annual Total Returns

For the periods ended April 30, 2021	Past 1 year	Life of fund^A
Fidelity® Series Treasury Bill Index Fund	0.13%	1.51%

^A From August 17, 2018

$10,000 Over Life of Fund

Let's say hypothetically that $10,000 was invested in Fidelity® Series Treasury Bill Index Fund on August 17, 2018, when the fund started.

The chart shows how the value of your investment would have changed, and also shows how the Bloomberg Barclays U.S. 3-6 Month Treasury Bill Index performed over the same period.

	Period Ending Values
	$10,413	Fidelity® Series Treasury Bill Index Fund
	$10,421	Bloomberg Barclays U.S. 3-6 Month Treasury Bill Index

Management's Discussion of Fund Performance

Market Recap: U.S. taxable investment-grade bonds posted a modest loss for the 12 months ending April 30, 2021, hampered by rising long-term market rates amid faster economic expansion in a risk-on market environment. The Bloomberg Barclays U.S. Aggregate Bond Index returned -0.27% for the period. Aggressive intervention by the U.S. Federal Reserve boosted market liquidity and led to a broad rally for fixed-income assets from the start of the period through July 2020. Long-term yields reached a historic low in August, and spreads widened modestly amid healthy issuance of new corporate bonds. Spreads then narrowed through period end and yields rose before moderating in April. In February 2021, yields rose notably because a $1.9 trillion COVID-relief bill offered hopes for a broad economic recovery but led to rising inflation expectations, which persisted through the end of April. Within the Bloomberg Barclays index, corporate bonds rose 4.46% for the 12 months, significantly topping the -4.32% return of U.S. Treasuries. Securitized sectors, meanwhile, posted a slight gain that outpaced Treasuries and the broader market. Outside the index, U.S. corporate high-yield bonds added 19.67% and Treasury Inflation-Protected Securities (TIPS) rose 6.09%.

Comments from Co-Portfolio Managers Brandon Bettencourt and Richard Munclinger: For the fiscal year, the Fidelity Series Treasury Bill Index Fund returned 0.13%. The fund’s result matched, net of fees, the return of the benchmark, the Bloomberg Barclays 3-6 Month Treasury Bill Index, and met our goal of producing monthly returns, before expenses, that closely match the benchmark’s returns. We use a method known as stratified sampling, which matches the index’s risk factors, but does not always hold all bonds in the exact proportions of the index. Early in the period, Treasury bills posted modest gains and yields fell as the U.S. Federal Reserve cut the federal funds rate and undertook massive quantitative easing to support the economy and the financial markets. Short-term yields declined more rapidly in February 2021 as the Fed maintained its program of asset purchases and continued to signal that it planned to keep the federal funds rate close to zero through the end of 2023. Yields ended the period near historic lows.

The views expressed above reflect those of the portfolio manager(s) only through the end of the period as stated on the cover of this report and do not necessarily represent the views of Fidelity or any other person in the Fidelity organization. Any such views are subject to change at any time based upon market or other conditions and Fidelity disclaims any responsibility to update such views. These views may not be relied on as investment advice and, because investment decisions for a Fidelity fund are based on numerous factors, may not be relied on as an indication of trading intent on behalf of any Fidelity fund.

Note to shareholders: On October 1, 2020, Richard Munclinger assumed co-management responsibilities for the fund, succeeding Jay Small.

Investment Summary (Unaudited)

Asset Allocation (% of fund's net assets)

As of April 30, 2021
	U.S. Government and U.S. Government Agency Obligations	99.9%
	Short-Term Investments and Net Other Assets (Liabilities)	0.1%

Schedule of Investments April 30, 2021

Showing Percentage of Net Assets

U.S. Government and Government Agency Obligations - 99.9%
	Principal Amount	Value
U.S. Treasury Obligations - 99.9%
U.S. Treasury Bills, yield at date of purchase 0.01% to 0.05% 8/5/21 to 10/28/21
(Cost $3,442,203,101)	3,442,533,000	3,442,274,747
TOTAL U.S. GOVERNMENT AND GOVERNMENT AGENCY OBLIGATIONS
(Cost $3,442,203,101)		3,442,274,747
	Shares	Value

Money Market Funds - 0.1%
Fidelity Cash Central Fund 0.04% (a)
(Cost $5,080,731)	5,079,716	5,080,731
TOTAL INVESTMENT IN SECURITIES - 100.0%
(Cost $3,447,283,832)		3,447,355,478
NET OTHER ASSETS (LIABILITIES) - 0.0%		(1,077,923)
NET ASSETS - 100%		$3,446,277,555

Legend

(a) Affiliated fund that is generally available only to investment companies and other accounts managed by Fidelity Investments. The rate quoted is the annualized seven-day yield of the fund at period end. A complete unaudited listing of the fund's holdings as of its most recent quarter end is available upon request. In addition, each Fidelity Central Fund's financial statements, which are not covered by the Fund's Report of Independent Registered Public Accounting Firm, are available on the SEC's website or upon request.

Affiliated Central Funds

Information regarding fiscal year to date income earned by the Fund from investments in Fidelity Central Funds is as follows:

Fund	Income earned
Fidelity Cash Central Fund	$4,539
Total	$4,539

Amounts in the income column in the above table include any capital gain distributions from underlying funds, which are presented in the corresponding line-item in the Statement of Operations, if applicable.

Investment Valuation

The following is a summary of the inputs used, as of April 30, 2021, involving the Fund's assets and liabilities carried at fair value. The inputs or methodology used for valuing securities may not be an indication of the risk associated with investing in those securities. For more information on valuation inputs, and their aggregation into the levels used below, please refer to the Investment Valuation section in the accompanying Notes to Financial Statements.

	Valuation Inputs at Reporting Date:
Description	Total	Level 1	Level 2	Level 3
Investments in Securities:
U.S. Government and Government Agency Obligations	$3,442,274,747	$--	$3,442,274,747	$--
Money Market Funds	5,080,731	5,080,731	--	--
Total Investments in Securities:	$3,447,355,478	$5,080,731	$3,442,274,747	$--

See accompanying notes which are an integral part of the financial statements.

Financial Statements

Statement of Assets and Liabilities

		April 30, 2021
Assets
Investment in securities, at value — See accompanying schedule: Unaffiliated issuers (cost $3,442,203,101)	$3,442,274,747
Fidelity Central Funds (cost $5,080,731)	5,080,731
Total Investment in Securities (cost $3,447,283,832)		$3,447,355,478
Receivable for investments sold		1,020,568,185
Receivable for fund shares sold		120,371,451
Distributions receivable from Fidelity Central Funds		192
Total assets		4,588,295,306
Liabilities
Payable for investments purchased	$1,141,984,613
Payable for fund shares redeemed	25,508
Other payables and accrued expenses	7,630
Total liabilities		1,142,017,751
Net Assets		$3,446,277,555
Net Assets consist of:
Paid in capital		$3,446,062,935
Total accumulated earnings (loss)		214,620
Net Assets		$3,446,277,555
Net Asset Value, offering price and redemption price per share ($3,446,277,555 ÷ 344,524,084 shares)		$10.00

See accompanying notes which are an integral part of the financial statements.

Statement of Operations

		Year ended April 30, 2021
Investment Income
Interest		$3,036,365
Income from Fidelity Central Funds		4,539
Total income		3,040,904
Expenses
Custodian fees and expenses	$26,431
Independent trustees' fees and expenses	7,921
Miscellaneous	2,597
Total expenses before reductions	36,949
Expense reductions	(119)
Total expenses after reductions		36,830
Net investment income (loss)		3,004,074
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers	2,058,182
Fidelity Central Funds	(427)
Total net realized gain (loss)		2,057,755
Change in net unrealized appreciation (depreciation) on:
Investment securities:
Unaffiliated issuers	(1,661,785)
Fidelity Central Funds	(119)
Total change in net unrealized appreciation (depreciation)		(1,661,904)
Net gain (loss)		395,851
Net increase (decrease) in net assets resulting from operations		$3,399,925

See accompanying notes which are an integral part of the financial statements.

Statement of Changes in Net Assets

	Year ended April 30, 2021	Year ended April 30, 2020
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$3,004,074	$26,958,717
Net realized gain (loss)	2,057,755	7,173,779
Change in net unrealized appreciation (depreciation)	(1,661,904)	1,718,982
Net increase (decrease) in net assets resulting from operations	3,399,925	35,851,478
Distributions to shareholders	(10,443,729)	(27,218,002)
Share transactions
Proceeds from sales of shares	1,648,546,820	1,706,513,777
Reinvestment of distributions	10,443,665	26,852,126
Cost of shares redeemed	(417,570,198)	(457,528,974)
Net increase (decrease) in net assets resulting from share transactions	1,241,420,287	1,275,836,929
Total increase (decrease) in net assets	1,234,376,483	1,284,470,405
Net Assets
Beginning of period	2,211,901,072	927,430,667
End of period	$3,446,277,555	$2,211,901,072
Other Information
Shares
Sold	164,748,562	170,579,768
Issued in reinvestment of distributions	1,044,006	2,683,799
Redeemed	(41,733,039)	(45,695,532)
Net increase (decrease)	124,059,529	127,568,035

See accompanying notes which are an integral part of the financial statements.

Financial Highlights

Fidelity Series Treasury Bill Index Fund


Years ended April 30,	2021	2020	2019 ^A
Selected Per–Share Data
Net asset value, beginning of period	$10.03	$9.98	$10.00
Income from Investment Operations
Net investment income (loss)^B	.011	.169	.166
Net realized and unrealized gain (loss)	.002	.062	(.005)
Total from investment operations	.013	.231	.161
Distributions from net investment income	(.012)	(.175)	(.181)
Distributions from net realized gain	(.031)	(.006)	–
Total distributions	(.043)	(.181)	(.181)
Net asset value, end of period	$10.00	$10.03	$9.98
Total Return^C,^D	.13%	2.34%	1.62%
Ratios to Average Net Assets^E,^F
Expenses before reductions^G	-%	-%	- %^H
Expenses net of fee waivers, if any^G	-%	-%	- %^H
Expenses net of all reductions^G	-%	-%	- %^H
Net investment income (loss)	.11%	1.69%	2.36%^H
Supplemental Data
Net assets, end of period (000 omitted)	$3,446,278	$2,211,901	$927,431

^A For the period August 17, 2018 (commencement of operations) to April 30, 2019.

^B Calculated based on average shares outstanding during the period.

^C Total returns for periods of less than one year are not annualized.

^D Total returns would have been lower if certain expenses had not been reduced during the applicable periods shown.

^E Fees and expenses of any underlying mutual funds or exchange-traded funds (ETFs) are not included in the Fund's expense ratio. The Fund indirectly bears its proportionate share of these expenses. For additional expense information related to investments in Fidelity Central Funds, please refer to the "Investments in Fidelity Central Funds" note found in the Notes to Financial Statements section of the most recent Annual or Semi-Annual report.

^F Expense ratios reflect operating expenses of the class. Expenses before reductions do not reflect amounts reimbursed, waived, or reduced through arrangements with the investment advisor, brokerage services, or other offset arrangements, if applicable, and do not represent the amount paid by the class during periods when reimbursements, waivers or reductions occur.

^G Amount represents less than .005%.

^H Annualized

See accompanying notes which are an integral part of the financial statements.

Notes to Financial Statements

For the period ended April 30, 2021

1. Organization.

Fidelity Series Treasury Bill Index Fund (the Fund) is a fund of Fidelity Hereford Street Trust (the Trust) and is authorized to issue an unlimited number of shares. Shares are offered only to certain other Fidelity funds and Fidelity managed 529 plans. The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Delaware statutory trust.

2. Investments in Fidelity Central Funds.

Funds may invest in Fidelity Central Funds, which are open-end investment companies generally available only to other investment companies and accounts managed by the investment adviser and its affiliates. The Schedule of Investments lists any Fidelity Central Funds held as an investment as of period end, but does not include the underlying holdings of each Fidelity Central Fund. An investing fund indirectly bears its proportionate share of the expenses of the underlying Fidelity Central Funds.

Based on its investment objective, each Fidelity Central Fund may invest or participate in various investment vehicles or strategies that are similar to those of the investing fund. These strategies are consistent with the investment objectives of the investing fund and may involve certain economic risks which may cause a decline in value of each of the Fidelity Central Funds and thus a decline in the value of the investing fund.

Fidelity Central Fund	Investment Manager	Investment Objective	Investment Practices	Expense Ratio^(a)
Fidelity Money Market Central Funds	Fidelity Management & Research Company LLC (FMR)	Each fund seeks to obtain a high level of current income consistent with the preservation of capital and liquidity.	Short-term Investments	Less than .005% to .01 %

(a) Expenses expressed as a percentage of average net assets and are as of each underlying Central Fund's most recent annual or semi-annual shareholder report.

A complete unaudited list of holdings for each Fidelity Central Fund is available upon request or at the Securities and Exchange Commission website at www.sec.gov. In addition, the financial statements of the Fidelity Central Funds, which are not covered by the Report of Independent Registered Public Accounting Firm, are available on the Securities and Exchange Commission website or upon request.

3. Significant Accounting Policies.

Investment Valuation. Investments are valued as of 4:00 p.m. Eastern time on the last calendar day of the period. The Board of Trustees (the Board) has delegated the day to day responsibility for the valuation of the Fund's investments to the Fair Value Committee (the Committee) established by the Fund's investment adviser. In accordance with valuation policies and procedures approved by the Board, the Fund attempts to obtain prices from one or more third party pricing vendors or brokers to value its investments. When current market prices, quotations or currency exchange rates are not readily available or reliable, investments will be fair valued in good faith by the Committee, in accordance with procedures adopted by the Board. Factors used in determining fair value vary by investment type and may include market or investment specific events, changes in interest rates and credit quality. The frequency with which these procedures are used cannot be predicted and they may be utilized to a significant extent. The Committee oversees the Fund's valuation policies and procedures and reports to the Board on the Committee's activities and fair value determinations. The Board monitors the appropriateness of the procedures used in valuing the Fund's investments and ratifies the fair value determinations of the Committee.

The Fund categorizes the inputs to valuation techniques used to value its investments into a disclosure hierarchy consisting of three levels as shown below:

Level 1 – quoted prices in active markets for identical investments
Level 2 – other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, etc.)
Level 3 – unobservable inputs (including the Fund's own assumptions based on the best information available)

Valuation techniques used to value the Fund's investments by major category are as follows:

Debt securities, including restricted securities, are valued based on evaluated prices received from third party pricing vendors or from brokers who make markets in such securities. U.S. government and government agency obligations are valued by pricing vendors who utilize matrix pricing which considers yield or price of bonds of comparable quality, coupon, maturity and type or by broker-supplied prices. When independent prices are unavailable or unreliable, debt securities may be valued utilizing pricing methodologies which consider similar factors that would be used by third party pricing vendors. Debt securities are generally categorized as Level 2 in the hierarchy but may be Level 3 depending on the circumstances.

Investments in open-end mutual funds, including the Fidelity Central Funds, are valued at their closing net asset value (NAV) each business day and are categorized as Level 1 in the hierarchy.

Changes in valuation techniques may result in transfers in or out of an assigned level within the disclosure hierarchy. The aggregate value of investments by input level as of April 30, 2021 is included at the end of the Fund's Schedule of Investments.

Investment Transactions and Income. For financial reporting purposes, the Fund's investment holdings and NAV include trades executed through the end of the last business day of the period. The NAV per share for processing shareholder transactions is calculated as of the close of business of the New York Stock Exchange (NYSE), normally 4:00 p.m. Eastern time and includes trades executed through the end of the prior business day. Gains and losses on securities sold are determined on the basis of identified cost. Income and capital gain distributions from Fidelity Central Funds, if any, are recorded on the ex-dividend date. Interest income is accrued as earned and includes coupon interest and amortization of premium and accretion of discount on debt securities as applicable.

Book-tax differences are primarily due to losses deferred due to wash sales.

As of period end, the cost and unrealized appreciation (depreciation) in securities, and derivatives if applicable, for federal income tax purposes were as follows:

Gross unrealized appreciation	$75,491
Gross unrealized depreciation	(3,845)
Net unrealized appreciation (depreciation)	$71,646
Tax Cost	$3,447,283,832

The tax-based components of distributable earnings as of period end were as follows:

Undistributed ordinary income	$142,974
Net unrealized appreciation (depreciation) on securities and other investments	$71,646

The tax character of distributions paid was as follows:

	April 30, 2021	April 30, 2020
Ordinary Income	$10,443,729	$ 27,218,002

4. Fees and Other Transactions with Affiliates.

Management Fee. Fidelity Management & Research Company LLC (the investment adviser) and its affiliates provide the Fund with investment management related services for which the Fund does not pay a management fee. Under the management contract, the investment adviser or an affiliate pays all ordinary operating expenses of the Fund, except custody fees, fees and expenses of the independent Trustees, and certain miscellaneous expenses such as proxy and shareholder meeting expenses.

5. Committed Line of Credit.

Certain Funds participate with other funds managed by the investment adviser or an affiliate in a $4.25 billion credit facility (the "line of credit") to be utilized for temporary or emergency purposes to fund shareholder redemptions or for other short-term liquidity purposes. The participating funds have agreed to pay commitment fees on their pro-rata portion of the line of credit, which are reflected in Miscellaneous expenses on the Statement of Operations, and are listed below. Effective during January 2021, commitment fees are borne by the investment advisor.

	Amount
Fidelity Series Treasury Bill Index Fund	$2,597

During the period, there were no borrowings on this line of credit.

6. Expense Reductions.

Through arrangements with the Fund's custodian, credits realized as a result of certain uninvested cash balances were used to reduce the Fund's expenses by $119.

7. Other.

At the end of the period, mutual funds and accounts managed by the investment adviser or its affiliates were the owners of record of all of the outstanding shares of the Fund.

8. Coronavirus (COVID-19) Pandemic.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Fidelity Hereford Street Trust and Shareholders of Fidelity Series Treasury Bill Index Fund

Opinion on the Financial Statements and Financial Highlights

We have audited the accompanying statement of assets and liabilities of Fidelity Series Treasury Bill Index Fund (the "Fund"), a fund of Fidelity Hereford Street Trust, including the schedule of investments, as of April 30, 2021, the related statement of operations for the year then ended, the statement of changes in net assets for each of the two years in the period then ended, the financial highlights for each of the two years in the period then ended and for the period from August 17, 2018 (commencement of operations) through April 30, 2019, and the related notes. In our opinion, the financial statements and financial highlights present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period then ended, and the financial highlights for each of the two years in the period then ended and for the period from August 17, 2018 (commencement of operations) through April 30, 2019, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements and financial highlights are the responsibility of the Fund's management. Our responsibility is to express an opinion on the Fund's financial statements and financial highlights based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements and financial highlights are free of material misstatement, whether due to error or fraud. The Fund is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Fund’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements and financial highlights, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements and financial highlights. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements and financial highlights. Our procedures included confirmation of securities owned as of April 30, 2021, by correspondence with the custodian and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

/s/ Deloitte & Touche LLP

Boston, Massachusetts

June 14, 2021

We have served as the auditor of one or more of the Fidelity investment companies since 1999.

Trustees and Officers

The fund’s Statement of Additional Information (SAI) includes more information about the Trustees. To request a free copy, call Fidelity at 1-800-544-8544.

The Trustees operate using a system of committees to facilitate the timely and efficient consideration of all matters of importance to the Trustees, the fund, and fund shareholders and to facilitate compliance with legal and regulatory requirements and oversight of the fund's activities and associated risks. The Board, acting through its committees, has charged FMR and its affiliates with (i) identifying events or circumstances the occurrence of which could have demonstrably adverse effects on the fund's business and/or reputation; (ii) implementing processes and controls to lessen the possibility that such events or circumstances occur or to mitigate the effects of such events or circumstances if they do occur; and (iii) creating and maintaining a system designed to evaluate continuously business and market conditions in order to facilitate the identification and implementation processes described in (i) and (ii) above. Because the day-to-day operations and activities of the fund are carried out by or through FMR, its affiliates, and other service providers, the fund's exposure to risks is mitigated but not eliminated by the processes overseen by the Trustees. While each of the Board's committees has responsibility for overseeing different aspects of the fund's activities, oversight is exercised primarily through the Operations and Audit Committees. In addition, an ad hoc Board committee of Independent Trustees has worked with FMR to enhance the Board's oversight of investment and financial risks, legal and regulatory risks, technology risks, and operational risks, including the development of additional risk reporting to the Board. Appropriate personnel, including but not limited to the fund's Chief Compliance Officer (CCO), FMR's internal auditor, the independent accountants, the fund's Treasurer and portfolio management personnel, make periodic reports to the Board's committees, as appropriate, including an annual review of Fidelity's risk management program for the Fidelity^® funds. The responsibilities of each standing committee, including their oversight responsibilities, are described further under "Standing Committees of the Trustees."

Interested Trustees*:

Correspondence intended for a Trustee who is an interested person may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Abigail P. Johnson (1961)

Year of Election or Appointment: 2009

Trustee

Chairman of the Board of Trustees

Jennifer Toolin McAuliffe (1959)

Year of Election or Appointment: 2016

Trustee

* Determined to be an “Interested Trustee” by virtue of, among other things, his or her affiliation with the trust or various entities under common control with FMR.

Independent Trustees:

Correspondence intended for an Independent Trustee may be sent to Fidelity Investments, P.O. Box 55235, Boston, Massachusetts 02205-5235.

Name, Year of Birth; Principal Occupations and Other Relevant Experience+

Elizabeth S. Acton (1951)

Year of Election or Appointment: 2013

Trustee

Ann E. Dunwoody (1953)

Year of Election or Appointment: 2018

Trustee

John Engler (1948)

Year of Election or Appointment: 2014

Trustee

Robert F. Gartland (1951)

Year of Election or Appointment: 2010

Trustee

Arthur E. Johnson (1947)

Year of Election or Appointment: 2008

Trustee

Chairman of the Independent Trustees

Michael E. Kenneally (1954)

Year of Election or Appointment: 2009

Trustee

Vice Chairman of the Independent Trustees

Marie L. Knowles (1946)

Year of Election or Appointment: 2001

Trustee

Mark A. Murray (1954)

Year of Election or Appointment: 2016

Trustee

Advisory Board Members and Officers:

Correspondence intended for an officer may be sent to Fidelity Investments, 245 Summer Street, Boston, Massachusetts 02210. Officers appear below in alphabetical order.

Name, Year of Birth; Principal Occupation

Robert W. Helm (1957)

Year of Election or Appointment: 2021

Member of the Advisory Board

Craig S. Brown (1977)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Brown also serves as Assistant Treasurer of other funds. Mr. Brown is an employee of Fidelity Investments (2013-present).

John J. Burke III (1964)

Year of Election or Appointment: 2018

Chief Financial Officer

David J. Carter (1973)

Year of Election or Appointment: 2020

Assistant Secretary

Mr. Carter also serves as Assistant Secretary of other funds. Mr. Carter serves as Vice President, Associate General Counsel (2010-present) and is an employee of Fidelity Investments (2005-present).

Jonathan Davis (1968)

Year of Election or Appointment: 2010

Assistant Treasurer

Laura M. Del Prato (1964)

Year of Election or Appointment: 2018

President and Treasurer

Colm A. Hogan (1973)

Year of Election or Appointment: 2016

Assistant Treasurer

Cynthia Lo Bessette (1969)

Year of Election or Appointment: 2019

Secretary and Chief Legal Officer (CLO)

Chris Maher (1972)

Year of Election or Appointment: 2013

Assistant Treasurer

Jamie Pagliocco (1964)

Year of Election or Appointment: 2020

Vice President

Kenneth B. Robins (1969)

Year of Election or Appointment: 2020

Chief Compliance Officer

Brett Segaloff (1972)

Year of Election or Appointment: 2021

Anti-Money Laundering (AML) Officer

Stacie M. Smith (1974)

Year of Election or Appointment: 2013

Assistant Treasurer

Marc L. Spector (1972)

Year of Election or Appointment: 2016

Deputy Treasurer

Jim Wegmann (1979)

Year of Election or Appointment: 2019

Assistant Treasurer

Mr. Wegmann also serves as Assistant Treasurer of other funds. Mr. Wegmann is an employee of Fidelity Investments (2011-present).

Shareholder Expense Example

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period (November 1, 2020 to April 30, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value November 1, 2020	Ending Account Value April 30, 2021	Expenses Paid During Period-^B November 1, 2020 to April 30, 2021
Fidelity Series Treasury Bill Index Fund	- %-^C
Actual		$1,000.00	$1,000.00	$--^D
Hypothetical-^E		$1,000.00	$1,024.79	$--^D

^A Annualized expense ratio reflects expenses net of applicable fee waivers.

^C Amount represents less than .005%.

^D Amount represents less than $.005.

^E 5% return per year before expenses

Distributions (Unaudited)

The Board of Trustees of Fidelity Series Treasury Bill Index Fund voted to pay on June 7, 2021, to shareholders of record at the opening of business on June 4, 2021, a distribution of $0.001 per share derived from capital gains realized from sales of portfolio securities.

A total of 99.91% of the dividends distributed during the fiscal year was derived from interest on U.S. Government securities which is generally exempt from state income tax.

The fund designates $11,686,598 of distributions paid in the calendar year 2020 as qualifying to be taxed as section 163(j) interest dividends.

The fund will notify shareholders in January 2022 of amounts for use in preparing 2021 income tax returns.

Liquidity Risk Management Program

The Securities and Exchange Commission adopted Rule 22e-4 under the Investment Company Act of 1940 (the Liquidity Rule) to promote effective liquidity risk management throughout the open-end investment company industry, thereby reducing the risk that funds will be unable to meet their redemption obligations and mitigating dilution of the interests of fund shareholders.

The Fund has adopted and implemented a liquidity risk management program pursuant to the Liquidity Rule (the Program) effective December 1, 2018. The Program is reasonably designed to assess and manage the Fund’s liquidity risk and to comply with the requirements of the Liquidity Rule. The Fund’s Board of Trustees (the Board) has designated the Fund’s investment adviser as administrator of the Program. The Fidelity advisers have established a Liquidity Risk Management Committee (the LRM Committee) to manage the Program for each of the Fidelity Funds. The LRM Committee monitors the adequacy and effectiveness of implementation of the Program and on a periodic basis assesses each Fund’s liquidity risk based on a variety of factors including (1) the Fund’s investment strategy, (2) portfolio liquidity and cash flow projections during normal and reasonably foreseeable stressed conditions, (3) shareholder redemptions, (4) borrowings and other funding sources and (5) in the case of exchange-traded funds, certain additional factors including the effect of the Fund’s prices and spreads, market participants, and basket compositions on the overall liquidity of the Fund’s portfolio, as applicable.

In accordance with the Program, each of the Fund’s portfolio investments is classified into one of four liquidity categories described below based on a determination of a reasonable expectation for how long it would take to convert the investment to cash (or sell or dispose of the investment) without significantly changing its market value.

Highly liquid investments – cash or convertible to cash within three business days or less
Moderately liquid investments – convertible to cash in three to seven calendar days
Less liquid investments – can be sold or disposed of, but not settled, within seven calendar days
Illiquid investments – cannot be sold or disposed of within seven calendar days

Liquidity classification determinations take into account a variety of factors including various market, trading and investment-specific considerations, as well as market depth, and generally utilize analysis from a third-party liquidity metrics service.

The Liquidity Rule places a 15% limit on a fund’s illiquid investments and requires funds that do not primarily hold assets that are highly liquid investments to determine and maintain a minimum percentage of the fund’s net assets to be invested in highly liquid investments (highly liquid investment minimum or HLIM). The Program includes provisions reasonably designed to comply with the 15% limit on illiquid investments and for determining, periodically reviewing and complying with the HLIM requirement as applicable.

At a recent meeting of the Fund’s Board of Trustees, the LRM Committee provided a written report to the Board pertaining to the operation, adequacy, and effectiveness of implementation of the Program for the annual period from December 1, 2019 through November 30, 2020. The report concluded that the Program has been implemented and is operating effectively and is reasonably designed to assess and manage the Fund’s liquidity risk.

Fidelity Investments

XSB-ANN-0621
1.9891219.102

Item 2.

Code of Ethics

As of the end of the period, April 30, 2021, Fidelity Hereford Street Trust (the trust) has adopted a code of ethics, as defined in Item 2 of Form N-CSR, that applies to its President and Treasurer and its Chief Financial Officer. A copy of the code of ethics is filed as an exhibit to this Form N-CSR.

Item 3.

Audit Committee Financial Expert

The Board of Trustees of the trust has determined that Elizabeth S. Acton is an audit committee financial expert, as defined in Item 3 of Form N-CSR. Ms. Acton is independent for purposes of Item 3 of Form N-CSR.

Item 4.

Principal Accountant Fees and Services

Fees and Services

The following table presents fees billed by Deloitte & Touche LLP, the member firms of Deloitte Touche Tohmatsu, and their respective affiliates (collectively, “Deloitte Entities”) in each of the last two fiscal years for services rendered to Fidelity Series Treasury Bill Index Fund (the “Fund”):

Services Billed by Deloitte Entities

April 30, 2021 Fees^A


	Audit Fees	Audit-Related Fees	Tax Fees	All Other Fees
Fidelity Series Treasury Bill Index Fund	$35,400	$-	$7,200	$900

April 30, 2020 Fees^A


	Audit Fees	Audit-Related Fees	Tax Fees	All Other Fees
Fidelity Series Treasury Bill Index Fund	$36,500	$-	$9,000	$800

^AAmounts may reflect rounding.

The following table presents fees billed by PricewaterhouseCoopers LLP (“PwC”) in each of the last two fiscal years for services rendered to Fidelity Flex Government Money Market Fund, Fidelity Government Money Market Fund, Fidelity Money Market Fund and Fidelity Treasury Only Money Market Fund (the “Funds”):

Services Billed by PwC

April 30, 2021 Fees^A


	Audit Fees	Audit-Related Fees	Tax Fees	All Other Fees
Fidelity Flex Government Money Market Fund	$37,600	$3,100	$1,900	$1,600
Fidelity Government Money Market Fund	$40,000	$3,200	$1,900	$1,600
Fidelity Money Market Fund	$36,100	$2,900	$1,900	$1,500
Fidelity Treasury Only Money Market Fund	$34,800	$2,800	$1,900	$1,400

April 30, 2020 Fees^A


	Audit Fees	Audit-Related Fees	Tax Fees	All Other Fees
Fidelity Flex Government Money Market Fund	$38,500	$3,200	$2,500	$1,700
Fidelity Government Money Market Fund	$40,900	$3,300	$1,900	$1,800
Fidelity Money Market Fund	$37,000	$3,000	$1,900	$1,700
Fidelity Treasury Only Money Market Fund	$35,700	$2,900	$1,900	$1,600

^AAmounts may reflect rounding.

The following table(s) present(s) fees billed by Deloitte Entities and PwC that were required to be approved by the Audit Committee for services that relate directly to the operations and financial reporting of the Fund(s) and that are rendered on behalf of Fidelity Management & Research Company LLC ("FMR") and entities controlling, controlled by, or under common control with FMR (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser) that provide ongoing services to the Fund(s) (“Fund Service Providers”):

Services Billed by Deloitte Entities


	April 30, 2021^A	April 30, 2020^A
Audit-Related Fees	$-	$-
Tax Fees	$-	$3,000
All Other Fees	$-	$-

^A Amounts may reflect rounding.

Services Billed by PwC


	April 30, 2021^A	April 30, 2020^A
Audit-Related Fees	$9,015,700	$8,884,200
Tax Fees	$14,300	$17,700
All Other Fees	$-	$-

^A Amounts may reflect rounding.

“Audit-Related Fees” represent fees billed for assurance and related services that are reasonably related to the performance of the fund audit or the review of the fund's financial statements and that are not reported under Audit Fees.

“Tax Fees” represent fees billed for tax compliance, tax advice or tax planning that relate directly to the operations and financial reporting of the fund.

“All Other Fees” represent fees billed for services provided to the fund or Fund Service Provider, a significant portion of which are assurance related, that relate directly to the operations and financial reporting of the fund, excluding those services that are reported under Audit Fees, Audit-Related Fees or Tax Fees.

Assurance services must be performed by an independent public accountant.

* * *

The aggregate non-audit fees billed by Deloitte Entities and PwC for services rendered to the Fund(s), FMR (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any Fund Service Provider for each of the last two fiscal years of the Fund(s) are as follows:


Billed By	April 30, 2021^A	April 30, 2020^A
Deloitte Entities	$529,700	$514,400
PwC	$14,176,400	$14,249,500

^A Amounts may reflect rounding.

The trust's Audit Committee has considered non-audit services that were not pre-approved that were provided by Deloitte Entities and PwC to Fund Service Providers to be compatible with maintaining the independence of Deloitte Entities and PwC in

its(their) audit of the Fund(s), taking into account representations from Deloitte Entities and PwC, in accordance with Public Company Accounting Oversight Board rules, regarding its independence from the Fund(s) and its(their) related entities and FMR’s review of the appropriateness and permissibility under applicable law of such non-audit services prior to their provision to the Fund(s) Service Providers.

Audit Committee Pre-Approval Policies and Procedures

The trust’s Audit Committee must pre-approve all audit and non-audit services provided by a fund’s independent registered public accounting firm relating to the operations or financial reporting of the fund. Prior to the commencement of any audit or non-audit services to a fund, the Audit Committee reviews the services to determine whether they are appropriate and permissible under applicable law.

The Audit Committee has adopted policies and procedures to, among other purposes, provide a framework for the Committee’s consideration of non-audit services by the audit firms that audit the Fidelity funds. The policies and procedures require that any non-audit service provided by a fund audit firm to a Fidelity fund and any non-audit service provided by a fund auditor to a Fund Service Provider that relates directly to the operations and financial reporting of a Fidelity fund (“Covered Service”) are subject to approval by the Audit Committee before such service is provided.

All Covered Services must be approved in advance of provision of the service either: (i) by formal resolution of the Audit Committee, or (ii) by oral or written approval of the service by the Chair of the Audit Committee (or if the Chair is unavailable, such other member of the Audit Committee as may be designated by the Chair to act in the Chair’s absence). The approval contemplated by (ii) above is permitted where the Treasurer determines that action on such an engagement is necessary before the next meeting of the Audit Committee.

Non-audit services provided by a fund audit firm to a Fund Service Provider that do not relate directly to the operations and financial reporting of a Fidelity fund are reported to the Audit Committee periodically.

Non-Audit Services Approved Pursuant to Rule 2-01(c)(7)(i)(C) and (ii) of Regulation S-X (“De Minimis Exception”)

There were no non-audit services approved or required to be approved by the Audit Committee pursuant to the De Minimis Exception during the Fund’s(s’) last two fiscal years relating to services provided to (i) the Fund(s) or (ii) any Fund Service Provider that relate directly to the operations and financial reporting of the Fund(s).

Item 5.

Audit Committee of Listed Registrants

Not applicable.

Item 6.

Investments

(a)

Not applicable.

(b)

Not applicable.

Item 7.

Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies

Not applicable.

Item 8.

Portfolio Managers of Closed-End Management Investment Companies

Not applicable.

Item 9.

Purchase of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers

Not applicable.

Item 10.

Submission of Matters to a Vote of Security Holders

There were no material changes to the procedures by which shareholders may recommend nominees to the trust’s Board of Trustees.

Item 11.

Controls and Procedures

(a)(i) The President and Treasurer and the Chief Financial Officer have concluded that the trust’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act) provide reasonable assurances that material information relating to the trust is made known to them by the appropriate persons, based on their evaluation of these controls and procedures as of a date within 90 days of the filing date of this report.

(a)(ii) There was no change in the trust’s internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act) that occurred during the period covered by this report that has materially affected, or is reasonably likely to materially affect, the trust’s internal control over financial reporting.

Item 12.

Disclosure of Securities Lending Activities for Closed-End Management

Investment Companies

Not applicable.

Item 13.

Exhibits


(a)	(1)	Code of Ethics pursuant to Item 2 of Form N-CSR is filed and attached hereto as EX-99.CODE ETH.
(a)	(2)	Certification pursuant to Rule 30a-2(a) under the Investment Company Act of 1940 (17 CFR 270.30a-2(a)) is filed and attached hereto as Exhibit 99.CERT.
(a)	(3)	Not applicable.
(b)		Certification pursuant to Rule 30a-2(b) under the Investment Company Act of 1940 (17 CFR 270.30a-2(b)) is furnished and attached hereto as Exhibit 99.906CERT.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Fidelity Hereford Street Trust


By:	/s/Laura M. Del Prato
	Laura M. Del Prato
	President and Treasurer

Date:	June 22, 2021

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.


By:	/s/Laura M. Del Prato
	Laura M. Del Prato
	President and Treasurer

Date:	June 22, 2021


By:	/s/John J. Burke III
	John J. Burke III
	Chief Financial Officer

Date:	June 22, 2021