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, MA 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:	October 31, 2021

Item 1.

Reports to Stockholders

Fidelity® Treasury Only Money Market Fund

Semi-Annual Report

October 31, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Shareholder Expense Example
Board Approval of Investment Advisory Contracts and Management Fees

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 COVID-19 emerged as a public health emergency that had a major influence on financial markets, primarily based on its impact on the global economy and corporate earnings. On March 11, 2020, the World Health Organization declared the COVID-19 outbreak a pandemic, citing sustained risk of further global spread. The pandemic prompted a number of measures to limit the spread of COVID-19, 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. To help stem the turmoil, the U.S. government took unprecedented action – in concert with the U.S. Federal Reserve and central banks around the world – to help support consumers, businesses, and the broader economy, and to limit disruption to the financial system.

In general, the overall impact of the pandemic lessened in 2021, amid a resilient economy and widespread distribution of three COVID-19 vaccines granted emergency use authorization from the U.S. Food and Drug Administration (FDA) early in the year. Still, the situation remains dynamic, and the extent and duration of its influence on financial markets and the economy is highly uncertain, due in part to a recent spike in cases based on highly contagious variants of the coronavirus.

Extreme events such as the COVID-19 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 continue to take extra steps to be responsive to customer needs. We encourage you to visit us online, where we offer ongoing updates, commentary, and analysis on the markets and our funds.

Investment Summary/Performance (Unaudited)

Effective Maturity Diversification as of October 31, 2021

Days	% of fund's investments 10/31/21
1 - 7	22.6
8 - 30	37.6
31 - 60	10.2
61 - 90	11.3
91 - 180	18.3

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 October 31, 2021
	U.S. Treasury Debt	95.0%
	Net Other Assets (Liabilities)	5.0%

Current 7-Day Yields

	10/31/21
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 October 31, 2021, the most recent period shown in the table, would have been (0.33)%.

Schedule of Investments October 31, 2021 (Unaudited)

Showing Percentage of Net Assets

U.S. Treasury Debt - 95.0%
	Yield(a)	Principal Amount (000s)	Value (000s)
U.S. Treasury Obligations - 95.0%
U.S. Treasury Bills
11/2/21 to 4/28/22	0.03 to 0.11%	$2,382,723	$2,382,506
U.S. Treasury Notes
11/15/21 to 10/31/23	0.05 to 0.21 (b)	1,044,536	1,045,468
TOTAL U.S. TREASURY DEBT
(Cost $3,427,974)			3,427,974
TOTAL INVESTMENT IN SECURITIES - 95.0%
(Cost $3,427,974)			3,427,974
NET OTHER ASSETS (LIABILITIES) - 5.0%			180,188
NET ASSETS - 100%			$3,608,162

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)		October 31, 2021 (Unaudited)
Assets
Investment in securities, at value — See accompanying schedule: Unaffiliated issuers (cost $3,427,974)		$3,427,974
Cash		199,011
Receivable for investments sold		113,100
Receivable for fund shares sold		1,001
Interest receivable		2,485
Total assets		3,743,571
Liabilities
Payable for investments purchased	$132,283
Payable for fund shares redeemed	2,918
Distributions payable	3
Accrued management fee	205
Total liabilities		135,409
Net Assets		$3,608,162
Net Assets consist of:
Paid in capital		$3,608,135
Total accumulated earnings (loss)		27
Net Assets		$3,608,162
Net Asset Value, offering price and redemption price per share ($3,608,162 ÷ 3,607,322 shares)		$1.00

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

Statement of Operations

Amounts in thousands		Six months ended October 31, 2021 (Unaudited)
Investment Income
Interest		$1,285
Expenses
Management fee	$7,770
Independent trustees' fees and expenses	4
Total expenses before reductions	7,774
Expense reductions	(6,677)
Total expenses after reductions		1,097
Net investment income (loss)		188
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		(38)
Total net realized gain (loss)		(38)
Net increase in net assets resulting from operations		$150

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

Statement of Changes in Net Assets

Amounts in thousands	Six months ended October 31, 2021 (Unaudited)	Year ended April 30, 2021
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$188	$434
Net realized gain (loss)	(38)	4
Net increase in net assets resulting from operations	150	438
Distributions to shareholders	(187)	(434)
Share transactions
Proceeds from sales of shares	660,178	1,481,386
Reinvestment of distributions	170	394
Cost of shares redeemed	(856,445)	(2,722,827)
Net increase (decrease) in net assets and shares resulting from share transactions	(196,097)	(1,241,047)
Total increase (decrease) in net assets	(196,134)	(1,241,043)
Net Assets
Beginning of period	3,804,296	5,045,339
End of period	$3,608,162	$3,804,296
Other Information
Shares
Sold	660,178	1,481,386
Issued in reinvestment of distributions	170	394
Redeemed	(856,445)	(2,722,827)
Net increase (decrease)	(196,097)	(1,241,047)

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

Financial Highlights

Fidelity Treasury Only Money Market Fund

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.014	.018	.008	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.014	.018	.008	–^A
Distributions from net investment income	–^A	–^A	(.014)	(.018)	(.008)	–^A
Total distributions	–^A	–^A	(.014)	(.018)	(.008)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.01%	1.39%	1.79%	.77%	.07%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.42%^F	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.06%^F	.15%	.42%	.42%	.42%	.38%
Expenses net of all reductions	.06%^F	.15%	.42%	.42%	.42%	.38%
Net investment income (loss)	.01%^F	.01%	1.27%	1.76%	.76%	.06%
Supplemental Data
Net assets, end of period (in millions)	$3,608	$3,804	$5,045	$2,823	$3,173	$3,720

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

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

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

^D 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.

^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.

Notes to Financial Statements (Unaudited)

For the period ended October 31, 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.

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. Interest income is accrued as earned and includes coupon interest and amortization of premium and accretion of discount on debt securities as applicable.

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. 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.

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	$3,427,974

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. During the period there were no interfund trades.

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 $6,676.

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 $1.

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.

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 (May 1, 2021 to October 31, 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. In addition, if these transactional costs were included, your costs would have been higher.

	Annualized Expense Ratio-^A	Beginning Account Value May 1, 2021	Ending Account Value October 31, 2021	Expenses Paid During Period-^B May 1, 2021 to October 31, 2021
Fidelity Treasury Only Money Market Fund	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**

^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 184/ 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 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 Treasury Only Money Market Fund	.42%
Actual		$2.12
Hypothetical-^(b)		$2.14

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

(b) 5% return per year before expenses

Board Approval of Investment Advisory Contracts and Management Fees

Fidelity Treasury Only Money Market Fund

Each year, the Board of Trustees, including the Independent Trustees (together, the Board), votes on the renewal of the management contract with Fidelity Management & Research Company LLC (FMR) and the sub-advisory agreements (together, the Advisory Contracts) for the fund. FMR and the sub-advisers are referred to herein as the Investment Advisers. The Board, assisted by the advice of fund counsel and Independent Trustees' counsel, requests and considers a broad range of information relevant to the renewal of the Advisory Contracts throughout the year.

The Board meets regularly and, at each of its meetings, covers an extensive agenda of topics and materials and considers factors that are relevant to its annual consideration of the renewal of the fund's Advisory Contracts, including the services and support provided to the fund and its shareholders. The Board has established four standing committees (Committees) — Operations, Audit, Fair Valuation, and Governance and Nominating — each composed of and chaired by Independent Trustees with varying backgrounds, to which the Board has assigned specific subject matter responsibilities in order to enhance effective decision-making by the Board. The Operations Committee, of which all of the Independent Trustees are members, meets regularly throughout the year and considers, among other matters, information specifically related to the annual consideration of the renewal of the fund's Advisory Contracts. The Board, acting directly and through its Committees, requests and receives information concerning the annual consideration of the renewal of the fund's Advisory Contracts. The Board also meets as needed to review matters specifically related to the Board's annual consideration of the renewal of the Advisory Contracts. Members of the Board may also meet with trustees of other Fidelity funds through joint ad hoc committees to discuss certain matters relevant to all of the Fidelity funds.

At its September 2021 meeting, the Board unanimously determined to renew the fund's Advisory Contracts. In reaching its determination, the Board considered all factors it believed relevant, including (i) the nature, extent, and quality of the services provided to the fund and its shareholders (including the investment performance of the fund); (ii) the competitiveness relative to peer funds of the fund's management fee and total expense ratio; (iii) the total costs of the services provided by and the profits realized by Fidelity from its relationships with the fund; and (iv) the extent to which, if any, economies of scale exist and are realized as the fund grows, and whether any economies of scale are appropriately shared with fund shareholders.

In considering whether to renew the Advisory Contracts for the fund, the Board reached a determination, with the assistance of fund counsel and Independent Trustees' counsel and through the exercise of its business judgment, that the renewal of the Advisory Contracts was in the best interests of the fund and its shareholders and that the compensation payable under the Advisory Contracts was fair and reasonable. The Board's decision to renew the Advisory Contracts was not based on any single factor, but rather was based on a comprehensive consideration of all the information provided to the Board at its meetings throughout the year. The Board, in reaching its determination to renew the Advisory Contracts, was aware that shareholders of the fund have a broad range of investment choices available to them, including a wide choice among funds offered by Fidelity's competitors, and that the fund's shareholders, who have the opportunity to review and weigh the disclosure provided by the fund in its prospectus and other public disclosures, have chosen to invest in this fund, which is part of the Fidelity family of funds.

Nature, Extent, and Quality of Services Provided. The Board considered Fidelity's staffing as it relates to the fund, including the backgrounds of investment personnel of Fidelity, and also considered the fund's investment objective, strategies, and related investment philosophy. The Independent Trustees also had discussions with senior management of Fidelity's investment operations and investment groups. The Board considered the structure of the investment personnel compensation program and whether this structure provides appropriate incentives to act in the best interests of the fund. Additionally, the Board considered the portfolio managers' investments, if any, in the funds that they manage. The Board also considered the steps Fidelity had taken to ensure the continued provision of high-quality services to the Fidelity funds during the COVID-19 pandemic, including the expansion of staff in client facing positions to maintain service levels in periods of high volumes and volatility.

Resources Dedicated to Investment Management and Support Services. The Board reviewed the general qualifications and capabilities of Fidelity's investment staff, including its size, education, experience, and resources, as well as Fidelity's approach to recruiting, training, managing, and compensating investment personnel. The Board noted the resources devoted to Fidelity's global investment organization, and that Fidelity's analysts have extensive resources, tools and capabilities that allow them to conduct sophisticated quantitative and fundamental analysis, as well as credit analysis of issuers, counterparties and guarantors. Further, the Board considered that Fidelity's investment professionals have sufficient access to global information and data so as to provide competitive investment results over time, and that those professionals also have access to sophisticated tools that permit them to assess portfolio construction and risk and performance attribution characteristics continuously, as well as to transmit new information and research conclusions rapidly around the world. Additionally, in its deliberations, the Board considered Fidelity's trading, risk management, compliance, cybersecurity, and technology and operations capabilities and resources, which are integral parts of the investment management process.

Shareholder and Administrative Services. The Board considered (i) the nature, extent, quality, and cost of advisory, administrative, and shareholder services performed by the Investment Advisers and their affiliates under the Advisory Contracts and under separate agreements covering transfer agency and pricing and bookkeeping services for the fund; (ii) the nature and extent of the supervision of third party service providers, principally custodians, subcustodians, and pricing vendors; and (iii) the resources devoted to, and the record of compliance with, the fund's compliance policies and procedures.

The Board noted that the growth of fund assets over time across the complex allows Fidelity to reinvest in the development of services designed to enhance the value and convenience of the Fidelity funds as investment vehicles. These services include 24-hour access to account information and market information over the Internet and through telephone representatives, investor education materials and asset allocation tools. The Board also considered that it reviews customer service metrics such as telephone response times, continuity of services on the website and metrics addressing services at Fidelity Investor Centers.

Investment in a Large Fund Family. The Board considered the benefits to shareholders of investing in a Fidelity fund, including the benefits of investing in a fund that is part of a large family of funds offering a variety of investment disciplines and providing a large variety of mutual fund investor services. The Board noted that Fidelity had taken, or had made recommendations to the Board that resulted in the Fidelity funds taking, a number of actions over the previous year that benefited particular funds, including: (i) continuing to dedicate additional resources to Fidelity's investment research process, which includes meetings with management of issuers of securities in which the funds invest; (ii) continuing efforts to enhance Fidelity's global research capabilities; (iii) launching new funds and ETFs with innovative structures, strategies and pricing and making other enhancements to meet client needs; (iv) launching new share classes of existing funds; (v) eliminating purchase minimums and broadening eligibility requirements for certain funds and share classes; (vi) reducing the holding period for the conversion of Class C shares to Class A shares; (vii) reducing management fees and total expenses for certain target date funds and classes and index funds; (viii) lowering expenses for certain existing funds and classes by implementing or lowering expense caps; (ix) rationalizing product lines and gaining increased efficiencies from fund mergers, liquidations, and share class consolidations; (x) continuing to develop, acquire and implement systems and technology to improve services to the funds and shareholders, strengthen information security, and increase efficiency; and (xi) continuing to implement enhancements to further strengthen Fidelity's product line to increase investors' probability of success in achieving their investment goals, including their retirement income goals.

The Board took into account discussions that occur at Board meetings throughout the year with representatives of the Investment Advisers about fund investment performance. In this regard the Board noted that as part of regularly scheduled fund reviews and other reports to the Board on fund performance, the Board considers annualized return information for the fund for different time periods, measured against an appropriate peer group of funds with similar objectives (peer group).

In addition to reviewing absolute and relative fund performance, the Independent Trustees periodically consider the appropriateness of fund performance metrics in evaluating the results achieved. In general, the Independent Trustees believe that fund performance should be evaluated based on gross performance (before fees and expenses but after transaction costs) compared to the gross performance of appropriate peer groups, over appropriate time periods that may include full market cycles, taking into account relevant factors including the following: general market conditions; expectations for interest rate levels and credit conditions; issuer-specific information including credit quality; the fund's market value NAV over time and its resilience under various stressed conditions; and fund cash flows and other factors. The Independent Trustees generally give greater weight to fund performance over longer time periods than over shorter time periods.

The Board recognizes that in interest rate environments where many competitors waive fees to maintain a minimum yield, relative money market fund performance on a net basis (after fees and expenses) may not be particularly meaningful due to miniscule performance differences among competitor funds. Depending on the circumstances, the Independent Trustees may be satisfied with a fund's performance notwithstanding that it lags its peer group for certain periods.

The Independent Trustees recognize that shareholders evaluate performance on a net basis over their own holding periods, for which one-, three-, and five-year periods are often used as a proxy. For this reason, the performance information reviewed by the Board also included net cumulative calendar year total return information for the fund and an appropriate peer group for the most recent one-, three-, and five-year periods. The Independent Trustees recognize that shareholders who are not investing through a tax-advantaged retirement account also consider tax consequences in evaluating performance.

Based on its review, the Board concluded that the nature, extent, and quality of services provided to the fund under the Advisory Contracts should continue to benefit the shareholders of the fund.

Competitiveness of Management Fee and Total Expense Ratio. The Board considered the fund's management fee and total expense ratio compared to "mapped groups" of competitive funds and classes created for the purpose of facilitating the Trustees' competitive analysis of management fees and total expenses. Fidelity creates "mapped groups" by combining similar Lipper investment objective categories that have comparable investment mandates. Combining Lipper investment objective categories aids the Board's management fee and total expense ratio comparisons by broadening the competitive group used for comparison.

Management Fee. The Board considered two proprietary management fee comparisons for the 12-month periods shown in basis points (BP) in the chart below. The group of Lipper funds used by the Board for management fee comparisons is referred to below as the "Total Mapped Group" and is broader than the Lipper peer group used by the Board for performance comparisons. The Total Mapped Group comparison focuses on a fund's standing in terms of gross management fees before expense reimbursements or caps relative to the total universe of funds with comparable investment mandates, regardless of whether their management fee structures also are comparable. Funds with comparable investment mandates offer exposure to similar types of securities. Funds with comparable management fee structures have similar management fee contractual arrangements (e.g., flat rate charged for advisory services, all-inclusive fee rate, etc.). "TMG %" represents the percentage of funds in the Total Mapped Group that had management fees that were lower than the fund's. For example, a hypothetical TMG % of 20% would mean that 80% of the funds in the Total Mapped Group had higher, and 20% had lower, management fees than the fund. The fund's actual TMG %s and the number of funds in the Total Mapped Group are in the chart below. The "Asset-Sized Peer Group" (ASPG) comparison focuses on a fund's standing relative to a subset of non-Fidelity funds within the Total Mapped Group that are similar in size and management fee structure. For example, if a fund is in the first quartile of the ASPG, the fund's management fee ranks in the least expensive or lowest 25% of funds in the ASPG. The ASPG represents at least 15% of the funds in the Total Mapped Group with comparable asset size and management fee structures, subject to a minimum of 50 funds (or all funds in the Total Mapped Group if fewer than 50). Additional information, such as the ASPG quartile in which the fund's management fee rate ranked, is also included in the chart and was considered by the Board. Because the vast majority of competitor funds' management fees do not cover expenses beyond portfolio, in prior years, the fund was compared on the basis of a hypothetical "net management fee," which was derived by subtracting payments made by Fidelity for expenses beyond portfolio management (including transfer agent fees, pricing and bookkeeping fees, and fees paid to non-affiliated custodians) from the fund's all-inclusive fee. Given the fund's competitive management fee rate, Fidelity no longer calculates a hypothetical net management fee for the fund and, as a result, the chart does not include a hypothetical net management fee for periods after 2016.

The Board noted that the fund's management fee rate ranked above the median of its Total Mapped Group and above the median of its ASPG for 2020. The Board also noted that the management fees of most competitor funds do not cover expenses beyond portfolio management, and that, excluding waivers and reimbursements, the fund's total expense ratio is below the median.

Based on its review, the Board concluded that the fund's management fee is fair and reasonable in light of the services that the fund receives and the other factors considered.

Total Expense Ratio. In its review of the fund's total expense ratio, the Board considered the fund's all-inclusive fee rate. The Board also considered other expenses, such as transfer agent fees, pricing and bookkeeping fees, and custodial, legal, and audit fees, paid by FMR under the all-inclusive arrangement. The Board also noted that Fidelity may agree to waive fees or reimburse expenses from time to time, and the extent to which, if any, it has done so for the fund. The fund is compared to those funds and classes in the Total Mapped Group (used by the Board for management fee comparisons) that have a similar sales load structure. The Board also considered a total expense ASPG comparison, which focuses on the total expenses of the fund relative to a subset of non-Fidelity funds within the similar sales load structure group. The total expense ASPG is limited to 15 larger and 15 smaller classes of different funds, where possible. The total expense ASPG comparison excludes performance adjustments and fund-paid 12b-1 fees to eliminate variability in expenses relating to these items.

The Board noted that the fund's total expense ratio ranked below the similar sales load structure group competitive median for 2020 and below the ASPG competitive median for 2020.

Fees Charged to Other Fidelity Clients. The Board also considered Fidelity fee structures and other information with respect to clients of Fidelity, such as other funds advised or subadvised by Fidelity, pension plan clients, and other institutional clients with similar mandates. The Board noted that a joint ad hoc committee created by it and the boards of other Fidelity funds periodically reviews and compares Fidelity's institutional investment advisory business with its business of providing services to the Fidelity funds and also noted the most recent findings of the committee. The Board noted that the committee's review included a consideration of the differences in services provided, fees charged, and costs incurred, as well as competition in the markets serving the different categories of clients.

Based on its review of total expense ratios and fees charged to other Fidelity clients, the Board concluded that the fund's total expense ratio was reasonable in light of the services that the fund and its shareholders receive and the other factors considered.

Costs of the Services and Profitability. The Board considered the revenues earned and the expenses incurred by Fidelity in conducting the business of developing, marketing, distributing, managing, administering and servicing the fund and servicing the fund's shareholders. The Board also considered the level of Fidelity's profits in respect of all the Fidelity funds.

On an annual basis, Fidelity presents to the Board information about the profitability of its relationships with the fund. Fidelity calculates profitability information for each fund, as well as aggregate profitability information for groups of Fidelity funds and all Fidelity funds, using a series of detailed revenue and cost allocation methodologies which originate with the books and records of Fidelity on which Fidelity's audited financial statements are based. The Audit Committee of the Board reviews any significant changes from the prior year's methodologies and the full Board approves such changes.

A public accounting firm has been engaged annually by the Board as part of the Board's assessment of Fidelity's profitability analysis. The engagement includes the review and assessment of the methodologies used by Fidelity in determining the revenues and expenses attributable to Fidelity's mutual fund business, and completion of agreed-upon procedures in respect of the mathematical accuracy of certain fund profitability information and its conformity to established allocation methodologies. After considering the reports issued under the engagement and information provided by Fidelity, the Board concluded that while other allocation methods may also be reasonable, Fidelity's profitability methodologies are reasonable in all material respects.

The Board also reviewed Fidelity's non-fund businesses and potential indirect benefits such businesses may have received as a result of their association with Fidelity's mutual fund business (i.e., fall-out benefits) as well as cases where Fidelity's affiliates may benefit from the funds' business. The Board considered areas where potential indirect benefits to the Fidelity funds from their relationships with Fidelity may exist. The Board's consideration of these matters was informed by the findings of a joint ad hoc committee created by it and the boards of other Fidelity funds to evaluate potential fall-out benefits.

The Board considered the costs of the services provided by and the profits realized by Fidelity in connection with the operation of the fund and was satisfied that the profitability was not excessive.

Economies of Scale. The Board considered whether there have been economies of scale in respect of the management of the Fidelity funds, whether the Fidelity funds (including the fund) have appropriately benefited from any such economies of scale, and whether there is potential for realization of any further economies of scale. The Board considered the extent to which the fund will benefit from economies of scale as assets grow through increased services to the fund, through waivers or reimbursements, or through fee or expense ratio reductions. The Board recognized that, due to the fund's current contractual arrangements, its expense ratio will not decline if the fund's operating costs decrease as assets grow, or rise as assets decrease. The Board also noted that a committee (the Economies of Scale Committee) created by it and the boards of other Fidelity funds periodically analyzes whether Fidelity attains economies of scale in respect of the management and servicing of the Fidelity funds, whether the Fidelity funds have appropriately benefited from such economies of scale, and whether there is potential for realization of any further economies of scale.

The Board concluded, taking into account the analysis of the Economies of Scale Committee, that economies of scale, if any, are being appropriately shared between fund shareholders and Fidelity.

Additional Information Requested by the Board. In order to develop fully the factual basis for consideration of the Fidelity funds' advisory contracts, the Board requested and received additional information on certain topics, including: (i) Fidelity's fund profitability methodology, profitability trends for certain funds, the allocation of various costs to different funds, and the impact of certain factors on fund profitability results; (ii) portfolio manager changes that have occurred during the past year and the amount of the investment that each portfolio manager has made in the Fidelity fund(s) that he or she manages; (iii) the extent to which current market conditions have affected retention and recruitment of personnel; (iv) the arrangements with and compensation paid to certain fund sub-advisers on behalf of the Fidelity funds and the treatment of such compensation within Fidelity's fund profitability methodology; (v) the terms of the funds' various management fee structures, including the basic group fee and the terms of Fidelity's voluntary expense limitation arrangements; (vi) Fidelity's transfer agent fee, expense, and service structures for different funds and classes relative to competitive trends; (vii) the impact on fund profitability of recent industry trends, such as the growth in passively managed funds and the continued waiver of money market fund fees; (viii) the types of management fee and total expense comparisons provided, and the challenges and limitations associated with such information; and (ix) explanations regarding the relative total expense ratios of certain funds and classes, total expense competitive trends and methodologies for total expense competitive comparisons. In addition, the Board considered its discussions with Fidelity regarding Fidelity's efforts to maintain the continuous investment and shareholder services necessary for the funds during the current pandemic and economic circumstances.

Based on its evaluation of all of the conclusions noted above, and after considering all factors it believed relevant, the Board concluded that the advisory fee arrangements are fair and reasonable, and that the fund's Advisory Contracts should be renewed.

Fidelity Investments

TMM-SANN-1221
1.538317.124

Fidelity® Money Market Fund

Semi-Annual Report

October 31, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Shareholder Expense Example
Board Approval of Investment Advisory Contracts and Management Fees

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 as of October 31, 2021

Days	% of fund's investments 10/31/21
1 - 7	41.6
8 - 30	4.9
31 - 60	16.6
61 - 90	11.7
91 - 180	18.9
> 180	6.3

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 October 31, 2021
	Certificates of Deposit	14.8%
	Commercial Paper	44.6%
	Variable Rate Demand Notes (VRDNs)	0.1%
	Non-Negotiable Time Deposit	15.4%
	Interfund Loans	0.1%
	Repurchase Agreements	25.5%
	Net Other Assets (Liabilities)^*	(0.5)%

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

Current 7-Day Yields

	10/31/21
Fidelity® Money Market Fund	0.01%
Premium Class	0.01%

Schedule of Investments October 31, 2021 (Unaudited)

Showing Percentage of Net Assets

Certificate of Deposit - 14.8%
	Yield(a)	Principal Amount (000s)	Value (000s)
Domestic Certificates Of Deposit - 0.4%
Bank of America NA
2/7/22	0.15%	$124,000	$124,000
New York Branch, Yankee Dollar, Foreign Banks - 14.4%
Bank of Montreal
1/3/22	0.16	167,000	167,000
Canadian Imperial Bank of Commerce
5/23/22	0.18	320,000	320,000
Credit Agricole CIB
12/6/21	0.12	228,000	228,000
Landesbank Baden-Wuerttemberg New York Branch
11/2/21 to 12/17/21	0.12 to 0.13	1,048,000	1,048,000
Mitsubishi UFJ Trust & Banking Corp.
1/24/22 to 2/16/22	0.14 to 0.16	344,000	344,000
Mizuho Corporate Bank Ltd.
12/1/21 to 12/13/21	0.11	476,000	476,000
Sumitomo Mitsui Banking Corp.
11/2/21 to 3/17/22	0.14 to 0.23	1,388,000	1,388,000
Svenska Handelsbanken, Inc.
5/2/22 to 5/27/22	0.17 to 0.20	610,000	610,000
Toronto-Dominion Bank
12/9/21 to 5/11/22	0.14 to 0.17 (b)	378,000	378,000
			4,959,000
TOTAL CERTIFICATE OF DEPOSIT
(Cost $5,083,000)			5,083,000

Financial Company Commercial Paper - 43.4%
ASB Finance Ltd. (London)
12/13/21 to 12/20/21	0.12 to 0.12	110,000	109,983
Bank of Montreal
2/14/22 to 5/6/22	0.15 to 0.17	1,359,000	1,358,092
BNP Paribas SA
11/3/21 to 2/7/22	0.12 to 0.13	645,000	644,910
BofA Securities, Inc.
4/13/22 to 5/9/22	0.16 to 0.18	327,000	326,737
BPCE SA
11/3/21 to 1/14/22	0.11 to 0.13	1,543,000	1,542,797
Caisse d'Amort de la Dette Sociale
12/9/21 to 4/14/22	0.14 to 0.17 (c)	1,504,000	1,503,533
Canadian Imperial Bank of Commerce
12/10/21 to 5/23/22	0.16 to 0.18	836,000	835,497
Federation des caisses Desjardin
3/3/22	0.15	41,000	40,979
ING U.S. Funding LLC (ING Bank NV Guaranteed)
12/10/21	0.11	103,000	102,988
Landesbank Baden-Wurttemberg
11/1/21	0.09	206,000	206,000
Lloyds Bank PLC
12/14/21 to 1/5/22	0.11 to 0.12	288,000	287,955
Mitsubishi UFJ Trust & Banking Corp.
11/15/21 to 1/12/22	0.12 to 0.14	668,000	667,897
Mizuho Bank Ltd. Singapore Branch
11/4/21 to 1/21/22	0.12 to 0.15	719,400	719,223
National Bank of Canada
1/18/22 to 4/13/22	0.15 to 0.17	1,278,000	1,277,355
Rabobank Nederland New York Branch
12/15/21	0.11	720,000	719,903
Royal Bank of Canada
1/24/22 to 4/8/22	0.15 to 0.17	1,462,000	1,461,265
Sumitomo Mitsui Banking Corp.
2/8/22	0.14	87,000	86,967
Sumitomo Mitsui Trust Bank Ltd.
11/1/21 to 1/21/22	0.13 to 0.15	1,468,000	1,467,650
Svenska Handelsbanken AB
11/10/21	0.14	144,000	143,995
The Toronto-Dominion Bank
2/18/22 to 7/15/22	0.15 to 0.21	1,355,000	1,353,930
Toyota Motor Credit Corp.
3/2/22	0.15	41,000	40,979
TOTAL FINANCIAL COMPANY COMMERCIAL PAPER
(Cost $14,898,635)			14,898,635

Asset Backed Commercial Paper - 1.2%
Atlantic Asset Securitization LLC (Liquidity Facility Credit Agricole CIB)

1/10/22	0.13	22,000	21,994
11/15/21	0.11	67,000	66,997
12/13/21	0.12	45,000	44,994
12/9/21	0.12	56,000	55,993
Sheffield Receivables Corp. (Liquidity Facility Barclays Bank PLC)

11/16/21	0.11	24,500	24,499
11/18/21	0.11	50,000	49,997
11/18/21	0.11	25,000	24,999
11/22/21	0.11	21,000	20,999
11/22/21	0.11	34,000	33,998
11/23/21	0.11	41,000	40,997
12/1/21	0.11	29,000	28,997
TOTAL ASSET BACKED COMMERCIAL PAPER
(Cost $414,464)			414,464

Variable Rate Demand Note - 0.1%
Florida - 0.1%
Florida Timber Fin. III LLC Taxable Series 2008, LOC Wells Fargo Bank NA, VRDN
11/5/21
(Cost $40,000)	0.08 (b)	40,000	40,000

Non-Negotiable Time Deposit - 15.4%
Time Deposits - 15.4%
Barclays Bank PLC
11/1/21	0.14	1,720,000	1,720,000
Bayerische Landesbank
11/1/21	0.08	309,000	309,000
Credit Agricole CIB
11/1/21	0.08	915,000	915,000
Credit Agricole CIB Paris Branch
11/1/21 to 11/3/21	0.11	577,000	577,000
Landesbank Hessen-Thuringen London Branch
11/1/21 to 11/5/21	0.12	1,351,000	1,351,000
Mizuho Bank Ltd. Canada Branch
11/1/21	0.08	418,000	418,000
TOTAL NON-NEGOTIABLE TIME DEPOSIT
(Cost $5,290,000)			5,290,000

Interfund Loans - 0.1%
	Principal Amount (000s)	Value (000s)
With:
Fidelity Pacific Basin Fund, at 0.32% due 11/1/21(d)
(Cost $17,815)	$17,815	$17,815
	Maturity Amount (000s)	Value (000s)

U.S. Government Agency Repurchase Agreement - 6.4%
In a joint trading account at 0.05% dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations) #
(Cost $2,202,547)	$2,202,557	$2,202,547

U.S. Treasury Repurchase Agreement - 10.6%
With:
Federal Reserve Bank of New York at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $3,592,014,972, 0.25% - 1.25%, 5/15/24 - 3/31/28)	3,592,015	3,592,000
Fixed Income Clearing Corp. - BNYM at 0.06%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $47,940,017, 0.38% - 3.00%, 2/15/22 - 11/15/44)	47,000	47,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $3,639,000)		3,639,000

Other Repurchase Agreement - 8.5%
Other Repurchase Agreement - 8.5%
With:
BMO Capital Markets Corp. at:
0.21%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $77,702,343, 1.95% - 5.81%, 10/21/27 - 9/1/51)	74,001	74,000
0.27%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $95,042,500, 4.50% - 8.00%, 2/15/23 - 2/15/29)	88,002	88,000
BMO Chicago Branch at 0.27%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $34,753,894, 0.00% - 15.50%, 12/15/21 - 7/20/71)	33,001	33,000
BNP Paribas Prime Brokerage, Inc. at:
0.37%, dated 10/29/21 due 11/1/21 (Collateralized by Equity Securities valued at $322,929,958)	299,009	299,000
0.53%, dated 9/1/21 due 11/1/21 (Collateralized by Equity Securities valued at $230,209,496)(b)(e)(f)	213,191	213,000
BofA Securities, Inc. at:
0.73%, dated 10/29/21 due 2/1/22 (Collateralized by Corporate Obligations valued at $115,475,014, 0.00% - 5.63%, 4/15/22 - 9/1/32)	107,271	107,000
0.78%, dated 10/18/21 due 2/1/22 (Collateralized by Corporate Obligations valued at $115,577,707, 0.13% - 5.75%, 4/1/22 - 6/1/48)	107,410	107,000
Credit Suisse Securities (U.S.A.) LLC at 0.5%, dated 9/17/21 due 1/3/22 (Collateralized by Corporate Obligations valued at $17,861,156, 0.75% - 6.08%, 4/22/30 - 2/25/66)	17,036	17,000
HSBC Securities, Inc. at 0.3%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $22,050,478, 1.88% - 8.00%, 10/7/22 - 6/19/49)	21,001	21,000
J.P. Morgan Securities, LLC at:
0.37%, dated 10/18/21 due 12/3/21 (Collateralized by Equity Securities valued at $70,210,103)(b)(e)(f)	65,038	65,000
0.42%, dated:
10/15/21 due 12/3/21
(Collateralized by Equity Securities valued at $230,085,633)(b)(e)(f)	213,149	213,000
(Collateralized by Equity Securities valued at $118,823,562)(b)(e)(f)	110,077	110,000
10/18/21 due 12/3/21 (Collateralized by Equity Securities valued at $252,970,119)(b)(e)(f)	235,156	235,000
Mitsubishi UFJ Securities (U.S.A.), Inc. at:
0.3%, dated 10/29/21 due 11/1/21 (Collateralized by Equity Securities valued at $115,354,668)	107,003	107,000
0.33%, dated:
10/27/21 due 11/3/21 (Collateralized by Equity Securities valued at $10,800,496)	10,001	10,000
10/28/21 due 11/4/21 (Collateralized by Equity Securities valued at $32,282,828)	30,002	30,000
0.59%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $8,640,619, 0.00% - 4.38%, 2/1/22 - 9/1/27)	8,000	8,000
Mizuho Securities U.S.A., Inc. at 0.34%, dated 10/29/21 due 11/1/21 (Collateralized by Equity Securities valued at $115,563,275)	107,003	107,000
RBS Securities, Inc. at 0.32%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $87,722,846, 0.13% - 3.51%, 3/9/23 - 6/11/40)	86,002	86,000
Societe Generale at:
0.21%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $138,316,673, 2.15% - 13.00%, 11/10/21 - 5/15/97)	128,002	128,000
0.24%, dated 10/26/21 due 11/2/21 (Collateralized by Corporate Obligations valued at $138,153,720, 2.25% - 13.00%, 11/10/21 - 5/15/97)	128,006	128,000
0.29%, dated 10/29/21 due 11/1/21 (Collateralized by Corporate Obligations valued at $92,872,912, 0.13% - 13.00%, 11/10/21 - 10/22/90)	86,002	86,000
0.32%, dated 10/26/21 due 11/2/21 (Collateralized by Corporate Obligations valued at $45,328,474, 0.28% - 13.00%, 11/10/21 - 6/5/2115)	42,003	42,000
Wells Fargo Securities, LLC at:
0.67%, dated:
9/3/21 due 12/2/21 (Collateralized by Corporate Obligations valued at $248,551,063, 0.48% - 6.40%, 11/4/21 - 12/6/47)	235,394	235,000
9/13/21 due 12/10/21 (Collateralized by Corporate Obligations valued at $139,447,631, 0.00% - 5.75%, 4/1/23 - 12/1/25)	129,211	129,000
0.68%, dated:
8/5/21 due 11/3/21 (Collateralized by Corporate Obligations valued at $137,388,127, 0.00% - 6.25%, 5/15/24 - 3/15/28)	127,216	127,000
8/9/21 due 11/5/21 (Collateralized by Corporate Obligations valued at $113,958,317, 0.00% - 4.95%, 2/1/22 - 2/15/30)	106,176	106,000
TOTAL OTHER REPURCHASE AGREEMENT
(Cost $2,911,000)		2,911,000
TOTAL INVESTMENT IN SECURITIES - 100.5%
(Cost $34,496,461)		34,496,461
NET OTHER ASSETS (LIABILITIES) - (0.5)%		(165,076)
NET ASSETS - 100%		$34,331,385

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.

(c) 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 $1,503,533,000 or 4.4% of net assets.

(d) Loan is with an affiliated fund.

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

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

Investment Valuation

Other Information

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

Repurchase Agreement / Counterparty	Value (000s)
$2,202,547,000 due 11/01/21 at 0.05%
BNY Mellon Capital Markets LLC	$144,519
Bank Of America, N.A.	185,161
Bank of America Securities, Inc.	205,734
Citigroup Global Markets, Inc.	77,150
Credit Agricole CIB New York Branch	107,592
Credit Suisse AG NY	9,270
HSBC Securities (USA), Inc.	23,145
ING Financial Markets LLC	10,428
JP Morgan Securities LLC	44,419
Mitsubishi UFJ Securities Holdings Ltd.	188,069
Mizuho Securities USA, Inc.	12,858
Nomura Securities International	302,944
RBC Dominion Securities, Inc.	25,717
Societe Generale	51,434
Sumitomo Mitsui Banking Corp. NY	500,362
Sumitomo Mitsui Banking Corp.	313,745
	$2,202,547

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)		October 31, 2021 (Unaudited)
Assets
Investment in securities, at value (including repurchase agreements of $8,752,547) — See accompanying schedule: Unaffiliated issuers (cost $34,478,646)	$34,478,646
Affiliated issuers (cost $17,815)	17,815
Total Investment in Securities (cost $34,496,461)		$34,496,461
Receivable for investments sold		84,075
Receivable for fund shares sold		15,637
Interest receivable		2,059
Prepaid expenses		50
Receivable from investment adviser for expense reductions		1,278
Other receivables		344
Total assets		34,599,904
Liabilities
Payable for investments purchased	$208,000
Payable for fund shares redeemed	54,564
Distributions payable	22
Accrued management fee	5,285
Other affiliated payables	137
Other payables and accrued expenses	511
Total liabilities		268,519
Net Assets		$34,331,385
Net Assets consist of:
Paid in capital		$34,331,257
Total accumulated earnings (loss)		128
Net Assets		$34,331,385
Net Asset Value and Maximum Offering Price
Fidelity Money Market Fund:
Net Asset Value, offering price and redemption price per share ($3,976,397 ÷ 3,975,964 shares)		$1.00
Premium Class:
Net Asset Value, offering price and redemption price per share ($30,354,988 ÷ 30,352,408 shares)		$1.00

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

Statement of Operations

Amounts in thousands		Six months ended October 31, 2021 (Unaudited)
Investment Income
Interest (including $38 from affiliated interfund lending)		$27,780
Expenses
Management fee	$45,818
Transfer agent fees	19,725
Accounting fees and expenses	828
Custodian fees and expenses	152
Independent trustees' fees and expenses	58
Registration fees	93
Audit	22
Legal	20
Miscellaneous	79
Total expenses before reductions	66,795
Expense reductions	(40,865)
Total expenses after reductions		25,930
Net investment income (loss)		1,850
Net increase in net assets resulting from operations		$1,850

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

Statement of Changes in Net Assets

Amounts in thousands	Six months ended October 31, 2021 (Unaudited)	Year ended April 30, 2021
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$1,850	$23,002
Net realized gain (loss)	–	8
Net increase in net assets resulting from operations	1,850	23,010
Distributions to shareholders	(1,848)	(23,003)
Share transactions - net increase (decrease)	(5,158,745)	(15,172,893)
Total increase (decrease) in net assets	(5,158,743)	(15,172,886)
Net Assets
Beginning of period	39,490,128	54,663,014
End of period	$34,331,385	$39,490,128

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

Financial Highlights

Fidelity Money Market Fund

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.016	.020	.011	.005
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.016	.020	.011	.005
Distributions from net investment income	–^A	–^A	(.016)	(.020)	(.011)	(.005)
Total distributions	–^A	–^A	(.016)	(.020)	(.011)	(.005)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.02%	1.61%	2.03%	1.11%	.52%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.42%^F	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.14%^F	.25%	.42%	.42%	.42%	.42%
Expenses net of all reductions	.14%^F	.25%	.42%	.42%	.42%	.42%
Net investment income (loss)	.01%^F	.03%	1.56%	2.06%	1.15%	.55%
Supplemental Data
Net assets, end of period (in millions)	$3,976	$4,430	$6,093	$5,196	$3,209	$2,301

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

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

^C 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.

Fidelity Money Market Fund Premium Class

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.017	.021	.012	.006
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.017	.021	.012	.006
Distributions from net investment income	–^A	–^A	(.017)	(.021)	(.012)	(.006)
Total distributions	–^A	–^A	(.017)	(.021)	(.012)	(.006)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.05%	1.73%	2.16%	1.23%	.64%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.35%^F	.36%	.36%	.37%	.37%	.37%
Expenses net of fee waivers, if any	.14%^F	.23%	.30%	.30%	.30%	.30%
Expenses net of all reductions	.14%^F	.23%	.30%	.30%	.30%	.30%
Net investment income (loss)	.01%^F	.05%	1.68%	2.18%	1.27%	.67%
Supplemental Data
Net assets, end of period (in millions)	$30,355	$35,060	$48,570	$36,981	$15,497	$7,317

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

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

^C 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 (Unaudited)

For the period ended October 31, 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)

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.

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

$344

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.

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	$34,496,461

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^(a)
Fidelity Money Market Fund	$3,482	.17
Premium Class	16,243	.10
	$19,725

(a) Annualized

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 annualized 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	$20,201	.31%

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 $8,760.

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 $2.

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	$5,886
Premium Class	26,217

5. Distributions to Shareholders.

Distributions to shareholders of each class were as follows:

	Six months ended October 31, 2021	Year ended April 30, 2021
Fidelity Money Market Fund
Distributions to shareholders
Fidelity Money Market Fund	$210	$1,355
Premium Class	1,638	21,648
Total	$1,848	$23,003

6. Share Transactions.

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

	Shares	Shares	Dollars	Dollars
	Six months ended October 31, 2021	Year ended April 30, 2021	Six months ended October 31, 2021	Year ended April 30, 2021
Fidelity Money Market Fund
Fidelity Money Market Fund
Shares sold	554,805	2,481,773	$554,805	$2,481,773
Reinvestment of distributions	195	1,248	195	1,248
Shares redeemed	(1,009,115)	(4,145,540)	(1,009,115)	(4,145,540)
Net increase (decrease)	(454,115)	(1,662,519)	$(454,115)	$(1,662,519)
Premium Class
Shares sold	2,520,025	17,649,816	$2,520,025	$17,649,816
Reinvestment of distributions	1,515	19,925	1,515	19,925
Shares redeemed	(7,226,170)	(31,180,115)	(7,226,170)	(31,180,115)
Net increase (decrease)	(4,704,630)	(13,510,374)	$(4,704,630)	$(13,510,374)

7. Other.

8. Coronavirus (COVID-19) Pandemic.

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 (May 1, 2021 to October 31, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value May 1, 2021	Ending Account Value October 31, 2021	Expenses Paid During Period-^B May 1, 2021 to October 31, 2021
Fidelity Money Market Fund
Fidelity Money Market Fund	.14%
Actual		$1,000.00	$1,000.10	$.71**
Hypothetical-^C		$1,000.00	$1,024.50	$.71**
Premium Class	.14%
Actual		$1,000.00	$1,000.10	$.71**
Hypothetical-^C		$1,000.00	$1,024.50	$.71**

^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 Money Market Fund
Fidelity Money Market Fund	.42%
Actual		$2.12
Hypothetical-^(b)		$2.14
Premium Class	.30%
Actual		$1.51
Hypothetical-^(b)		$1.53

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

(b) 5% return per year before expenses

Board Approval of Investment Advisory Contracts and Management Fees

Fidelity Money Market Fund

At its September 2021 meeting, the Board unanimously determined to renew the fund's Advisory Contracts. In reaching its determination, the Board considered all factors it believed relevant, including (i) the nature, extent, and quality of the services provided to the fund and its shareholders (including the investment performance of the fund); (ii) the competitiveness relative to peer funds of the fund's management fee and total expense ratio of a representative class (Premium Class); (iii) the total costs of the services provided by and the profits realized by Fidelity from its relationships with the fund; and (iv) the extent to which, if any, economies of scale exist and are realized as the fund grows, and whether any economies of scale are appropriately shared with fund shareholders.

Nature, Extent, and Quality of Services Provided. The Board considered Fidelity's staffing as it relates to the fund, including the backgrounds of investment personnel of Fidelity, and also considered the fund's investment objective, strategies, and related investment philosophy. The Independent Trustees also had discussions with senior management of Fidelity's investment operations and investment groups. The Board considered the structure of the investment personnel compensation program and whether this structure provides appropriate incentives to act in the best interests of the fund. Additionally, the Board considered the portfolio managers' investments, if any, in the funds that they manage. The Board also considered the steps Fidelity had taken to ensure the continued provision of high quality services to the Fidelity funds during the COVID-19 pandemic, including the expansion of staff in client facing positions to maintain service levels in periods of high volumes and volatility.

Based on its review, the Board concluded that the nature, extent, and quality of services provided to the fund under the Advisory Contracts should continue to benefit the shareholders of the fund.

Management Fee. The Board considered two proprietary management fee comparisons for the 12-month periods shown in basis points (BP) in the chart below. The group of Lipper funds used by the Board for management fee comparisons is referred to below as the "Total Mapped Group" and is broader than the Lipper peer group used by the Board for performance comparisons. The Total Mapped Group comparison focuses on a fund's standing in terms of gross management fees before expense reimbursements or caps relative to the total universe of funds with comparable investment mandates, regardless of whether their management fee structures also are comparable. Funds with comparable investment mandates offer exposure to similar types of securities. Funds with comparable management fee structures have similar management fee contractual arrangements (e.g., flat rate charged for advisory services, all-inclusive fee rate, etc.). "TMG %" represents the percentage of funds in the Total Mapped Group that had management fees that were lower than the fund's. For example, a hypothetical TMG % of 20% would mean that 80% of the funds in the Total Mapped Group had higher, and 20% had lower, management fees than the fund. The fund's actual TMG %s and the number of funds in the Total Mapped Group are in the chart below. The "Asset-Sized Peer Group" (ASPG) comparison focuses on a fund's standing relative to a subset of non-Fidelity funds within the Total Mapped Group that are similar in size and management fee structure. For example, if a fund is in the first quartile of the ASPG, the fund's management fee ranks in the least expensive or lowest 25% of funds in the ASPG. The ASPG represents at least 15% of the funds in the Total Mapped Group with comparable asset size and management fee structures, subject to a minimum of 50 funds (or all funds in the Total Mapped Group if fewer than 50). Additional information, such as the ASPG quartile in which the fund's management fee rate ranked, is also included in the chart and was considered by the Board.

The Board noted that the fund's management fee rate ranked below the median of its Total Mapped Group and above the median of its ASPG for 2020. The Board also noted that the fund's management fee ranks 2 BPS above the ASPG median, but that Fidelity believes that the fund's total expense ratio provides a more meaningful comparison of fees due to varying expense structures. The Board also noted that, excluding waivers and 12b-1 fees, the total expense ratio of the representative class of the fund is below the ASPG median.

Based on its review, the Board concluded that the fund's management fee is fair and reasonable in light of the services that the fund receives and the other factors considered.

Total Expense Ratio. In its review of the total expense ratio of the representative class (Premium Class) of the fund, the Board considered the fund's management fee rate as well as other fund or class expenses, as applicable, such as transfer agent fees, pricing and bookkeeping fees, and custodial, legal, and audit fees. The Board also noted that Fidelity may agree to waive fees or reimburse expenses from time to time, and the extent to which, if any, it has done so for the fund. The representative class is compared to those funds and classes in the Total Mapped Group (used by the Board for management fee comparisons) that have a similar sales load structure. The Board also considered a total expense ASPG comparison, which focuses on the total expenses of the representative class relative to a subset of non-Fidelity funds within the similar sales load structure group. The total expense ASPG is limited to 15 larger and 15 smaller classes in fund average assets for a total of 30 classes, where possible. The total expense ASPG comparison excludes performance adjustments and fund-paid 12b-1 fees to eliminate variability in expenses relating to these items.

The Board noted that the total expense ratio of Premium Class ranked below the competitive median of the similar sales load structure group for 2020 and below the ASPG competitive median for 2020.

The Board further considered that current contractual arrangements for the fund oblige FMR to pay all "class-level" expenses of the retail class of the fund to the extent necessary to limit total operating expenses, with certain exceptions, to 0.42%. These contractual arrangements may not be amended to increase the fees or expenses payable except by a vote of a majority of the Board and by a vote of a majority of the outstanding voting securities of the class. The Board further considered that FMR has contractually agreed to reimburse Premium Class of the fund to the extent that total operating expenses, with certain exceptions, as a percentage of its average net assets, exceed 0.30% through August 31, 2022.

Based on its review of total expense ratios and fees charged to other Fidelity clients, the Board concluded that the total expense ratio of each class of the fund was reasonable in light of the services that the fund and its shareholders receive and the other factors considered.

Economies of Scale. The Board considered whether there have been economies of scale in respect of the management of the Fidelity funds, whether the Fidelity funds (including the fund) have appropriately benefited from any such economies of scale, and whether there is potential for realization of any further economies of scale. The Board considered the extent to which the fund will benefit from economies of scale as assets grow through increased services to the fund, through waivers or reimbursements, or through fee or expense ratio reductions. The Board recognized that, due to the fund's current contractual arrangements, the expense ratio of the retail class will not decline if the class's operating costs decrease as assets grow, or rise as assets decrease. The Board also noted that a committee (the Economies of Scale Committee) created by it and the boards of other Fidelity funds periodically analyzes whether Fidelity attains economies of scale in respect of the management and servicing of the Fidelity funds, whether the Fidelity funds have appropriately benefited from such economies of scale, and whether there is potential for realization of any further economies of scale.

The Board concluded, taking into account the analysis of the Economies of Scale Committee, that economies of scale, if any, are being appropriately shared between fund shareholders and Fidelity.

Fidelity Investments

SPM-SANN-1221
1.538241.124

Fidelity® Government Money Market Fund

Semi-Annual Report

October 31, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Shareholder Expense Example
Board Approval of Investment Advisory Contracts and Management Fees

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 10/31/21
1 - 7	70.1
8 - 30	7.5
31 - 60	1.9
61 - 90	4.6
91 - 180	9.8
>180	6.8

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 October 31, 2021
	U.S. Treasury Debt	31.7%
	U.S. Government Agency Debt	9.7%
	Repurchase Agreements	58.6%
	Variable Rate Demand Notes (VRDNs)	0.1%
	Net Other Assets (Liabilities)^*	(0.1)%

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

Current 7-Day Yields

	10/31/21
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 October 31, 2021 (Unaudited)

Showing Percentage of Net Assets

U.S. Treasury Debt - 31.7%
	Yield(a)	Principal Amount	Value
U.S. Treasury Obligations - 31.7%
U.S. Treasury Bills
11/2/21 to 10/6/22	0.05 to 0.12%	$31,546,803,700	$31,541,543,438
U.S. Treasury Bonds
11/15/21	0.05 to 0.11	239,000,000	239,722,334
U.S. Treasury Notes
10/31/21 to 10/31/23	0.03 to 0.21 (b)	42,046,963,800	42,239,165,964
TOTAL U.S. TREASURY DEBT
(Cost $74,020,431,736)			74,020,431,736

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, 0.06% 11/5/21, LOC Freddie Mac, VRDN
11/5/21	0.06 (b)(c)	9,700,000	9,700,000
New York - 0.1%
FHLMC New York City Hsg. Dev. Corp. Multi-family Mtg. Rev. Series 2011 A, 0.07% 11/5/21, LOC Freddie Mac, VRDN
11/5/21	0.07 (b)(c)	13,700,000	13,700,000
FHLMC New York Hsg. Fin. Agcy. Rev. (Clinton Green North Hsg. Proj.) Series 2005 A, 0.07% 11/5/21, LOC Freddie Mac, VRDN
11/5/21	0.07 (b)(c)	35,445,000	35,445,000
FHLMC New York Hsg. Fin. Agcy. Rev. (Clinton Green South Hsg. Proj.) Series 2005 A, 0.07% 11/5/21, LOC Freddie Mac, VRDN
11/5/21	0.07 (b)(c)	16,900,000	16,900,000
FHLMC New York Hsg. Fin. Agcy. Rev. (Theatre Row Tower Hsg. Proj.) Series 2000 A, 0.07% 11/5/21, LOC Freddie Mac, VRDN
11/5/21	0.07 (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, 0.07% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.07 (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, 0.06% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.06 (b)(c)	24,800,000	24,800,000
FNMA New York Hsg. Fin. Agcy. Rev. (250 West 50th Street Hsg. Proj.) Series 1997 A, 0.06% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.06 (b)(c)	23,600,000	23,600,000
FNMA New York Hsg. Fin. Agcy. Rev. (316 Eleventh Ave. Hsg. Proj.) Series 2007 A, 0.07% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.07 (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, 0.07% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.07 (b)(c)	48,350,000	48,350,000
FNMA New York Hsg. Fin. Agcy. Rev. (Tribeca Park Proj.) Series 1997 A, 0.07% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.07 (b)(c)	11,400,000	11,400,000
FNMA New York Hsg. Fin. Agcy. Rev. (West 23rd Street Hsg. Proj.) Series 2001 A, 0.06% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.06 (b)(c)	6,500,000	6,500,000
FNMA New York Hsg. Fin. Agcy. Rev. Series 1997 A, 0.07% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.07 (b)(c)	10,200,000	10,200,000
FNMA New York Hsg. Fin. Agcy. Rev. Series 2008 A, 0.09% 11/5/21, LOC Fannie Mae, VRDN
11/5/21	0.09 (b)(c)	14,800,000	14,800,000
			252,395,000
TOTAL VARIABLE RATE DEMAND NOTE
(Cost $262,095,000)			262,095,000

U.S. Government Agency Debt - 9.7%
Federal Agencies - 9.7%
Fannie Mae
12/10/21 to 7/29/22	0.06 to 0.35 (b)	4,592,555,000	4,592,633,783
Federal Farm Credit Bank
12/13/21 to 9/19/22	0.06 to 0.10 (b)	1,017,750,000	1,017,714,540
Federal Home Loan Bank
11/4/21 to 12/15/22	0.05 to 0.22 (b)	11,877,415,000	11,877,705,580
3/29/22	0.06	290,000,000	289,994,014
3/29/22	0.06	77,000,000	76,998,383
Freddie Mac
12/10/21 to 9/9/22	0.06 to 0.25 (b)	4,843,440,000	4,843,550,334
TOTAL U.S. GOVERNMENT AGENCY DEBT
(Cost $22,698,596,634)			22,698,596,634

U.S. Government Agency Repurchase Agreement - 11.8%
	Maturity Amount	Value
In a joint trading account at:
0.05% dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations ) #	$14,071,378,896	$14,071,315,000
0.05% dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations) #	52,000,217	52,000,000
With:
ABN AMRO Bank NV at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $540,602,253, 1.94% - 5.50%, 9/1/28 - 9/20/51)	530,002,208	530,000,000
Barclays Bank PLC at 0.05%, dated 10/29/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $80,580,336, 2.50%, 7/20/51)	79,000,768	79,000,000
BMO Harris Bank NA at 0.06%, dated:
9/1/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $199,938,632, 2.00% - 6.00%, 5/1/26 - 6/15/60)	196,027,249	196,000,000
9/7/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $140,772,903, 1.50% - 8.00%, 9/20/24 - 10/15/61)	138,041,630	138,000,000
9/13/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $100,987,560, 1.50% - 3.75%, 7/1/25 - 10/15/61)	99,013,764	99,000,000
CIBC Bank U.S.A. at:
0.06%, dated 8/6/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $296,904,579, 0.00% - 5.50%, 6/30/23 - 8/15/51)	291,080,025	291,000,000
0.09%, dated 10/26/21 due 1/24/22 (Collateralized by U.S. Government Obligations valued at $80,896,985, 0.00% - 6.55%, 4/30/22 - 5/1/51)	79,017,775	79,000,000
Citibank NA at 0.06%, dated 10/26/21 due 11/2/21
(Collateralized by U.S. Treasury Obligations valued at $602,136,337, 0.00% - 8.00%, 11/2/21 - 5/20/51)	590,006,883	590,000,000
(Collateralized by U.S. Treasury Obligations valued at $100,109,178, 0.00% - 8.88%, 11/15/21 - 8/15/51)	98,001,143	98,000,000
Citigroup Global Capital Markets, Inc. at 0.06%, dated 10/26/21 due 11/2/21 (Collateralized by U.S. Government Obligations valued at $400,864,143, 1.38% - 4.00%, 2/15/44 - 10/20/51)	393,004,585	393,000,000
Deutsche Bank AG, New York at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $202,041,831, 2.38% - 6.50%, 6/15/24 - 9/15/28)	197,000,821	197,000,000
Deutsche Bank Securities, Inc. at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $404,791,687, 3.25% - 3.75%, 11/15/46 - 3/15/50)	393,001,638	393,000,000
Goldman Sachs & Co. at:
0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $99,960,417, 2.00% - 4.50%, 5/20/34 - 2/20/51)	98,000,408	98,000,000
0.06%, dated 10/28/21 due 11/4/21 (Collateralized by U.S. Government Obligations valued at $1,607,529,824, 1.50% - 5.00%, 11/15/40 - 6/15/61)	1,576,016,854	1,576,000,000
Mitsubishi UFJ Securities (U.S.A.), Inc. at 0.07%, dated:
10/5/21 due 12/6/21 (Collateralized by U.S. Government Obligations valued at $260,124,364, 1.91% - 6.00%, 1/1/24 - 10/1/51)	255,030,742	255,000,000
10/12/21 due 12/13/21 (Collateralized by U.S. Government Obligations valued at $300,911,702, 1.76% - 6.00%, 12/1/21 - 10/1/51)	295,035,564	295,000,000
10/19/21 due 12/17/21 (Collateralized by U.S. Government Obligations valued at $202,069,865, 0.00% - 5.54%, 1/1/24 - 11/1/51)	198,022,715	198,000,000
10/27/21 due 12/23/21 (Collateralized by U.S. Government Obligations valued at $200,941,954, 1.50% - 5.00%, 9/1/31 - 10/1/51)	197,021,834	197,000,000
RBC Dominion Securities at:
0.05%, dated:
8/24/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $400,991,957, 0.00% - 6.00%, 11/15/21 - 7/1/51)	393,062,225	393,000,000
9/3/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $201,920,562, 0.00% - 6.00%, 11/30/21 - 10/1/51)	197,024,899	197,000,000
9/10/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $400,694,625, 0.00% - 6.13%, 1/20/22 - 6/20/51)	392,049,544	392,000,000
9/17/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $534,654,649, 0.00% - 6.00%, 1/20/22 - 8/1/51)	524,066,228	524,000,000
9/20/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $402,619,170, 0.00% - 6.00%, 1/20/22 - 10/1/51)	393,049,671	393,000,000
0.06%, dated:
10/13/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $201,257,723, 0.00% - 6.00%, 1/20/22 - 7/20/51)	197,030,207	197,000,000
10/14/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $402,795,273, 0.00% - 4.00%, 11/15/21 - 5/20/51)	393,060,260	393,000,000
10/29/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $200,941,015, 0.63% - 2.75%, 11/30/21 - 2/15/45)	197,030,863	197,000,000
RBC Financial Group at 0.06%, dated:
6/25/21 due 11/5/21
(Collateralized by U.S. Government Obligations valued at $198,289,251, 0.00% - 7.60%, 12/16/21 - 1/1/58)	194,069,193	194,000,000
(Collateralized by U.S. Government Obligations valued at $991,124,171, 1.25% - 7.00%, 12/15/23 - 8/1/58)	971,347,942	971,000,000
6/29/21 due 11/5/21
(Collateralized by U.S. Government Obligations valued at $395,857,830, 1.25% - 6.00%, 11/1/27 - 8/1/59)	388,137,093	388,000,000
(Collateralized by U.S. Government Obligations valued at $790,896,086, 2.00% - 6.50%, 12/15/23 - 7/1/60)	775,275,125	775,000,000
(Collateralized by U.S. Government Obligations valued at $790,664,688, 2.00% - 5.50%, 8/1/25 - 1/1/58)	775,279,000	775,000,000
6/30/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $213,224,057, 0.63% - 6.50%, 1/31/22 - 8/1/59)	209,075,240	209,000,000
8/6/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $197,959,871, 2.00% - 4.50%, 1/1/27 - 8/1/58)	194,067,900	194,000,000
Sumitomo Mitsui Trust Bank Ltd. at:
0.09%, dated:
9/27/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $61,427,571, 0.38% - 3.00%, 3/31/22 - 10/20/46)	60,012,900	60,000,000
10/1/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $67,013,249, 0.38% - 3.50%, 3/31/22 - 12/1/47)	65,600,576	65,585,000
10/15/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $124,485,404, 0.38% - 4.00%, 3/31/22 - 6/1/48)	122,027,755	122,000,000
11/1/21 due 11/5/21(d)	128,365,767	128,336,250
0.1%, dated 8/2/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $155,107,143, 0.38% - 4.00%, 3/31/22 - 8/1/49)	152,038,422	152,000,000
TD Securities (U.S.A.) at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations valued at $880,263,668, 2.00% - 4.50%, 5/1/35 - 11/1/51)	863,003,596	863,000,000
TOTAL U.S. GOVERNMENT AGENCY REPURCHASE AGREEMENT
(Cost $27,408,236,250)		27,408,236,250

U.S. Treasury Repurchase Agreement - 46.8%
With:
ABN AMRO Bank NV at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $509,546,702, 0.13% - 3.13%, 1/31/22 - 5/15/51)	497,002,071	497,000,000
Barclays Bank PLC at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $546,722,370, 0.00% - 2.25%, 3/24/22 - 5/15/40)	536,002,233	536,000,000
BMO Capital Markets Corp. at 0.06%, dated 10/12/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $181,572,062, 0.00% - 8.00%, 11/15/21 - 8/15/51)	178,025,019	178,000,000
BMO Harris Bank NA at 0.06%, dated:
9/24/21 due 11/5/21
(Collateralized by U.S. Treasury Obligations valued at $90,956,000, 0.09% - 3.88%, 5/15/22 - 11/15/48)	89,008,294	89,000,000
(Collateralized by U.S. Treasury Obligations valued at $91,404,602, 0.09% - 2.63%, 7/31/22 - 5/15/51)	89,012,102	89,000,000
10/14/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $181,746,683, 0.00% - 3.38%, 11/18/21 - 8/15/51)	178,026,107	178,000,000
11/1/21 due 11/5/21(d)	107,024,075	107,000,000
BNP Paribas, SA at 0.05%, dated:
10/15/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $1,180,713,143, 0.00% - 6.50%, 11/4/21 - 5/15/51)	1,157,027,318	1,157,000,000
10/18/21 due 11/2/21 (Collateralized by U.S. Treasury Obligations valued at $908,034,230, 0.00% - 6.50%, 1/31/22 - 2/15/51)	890,018,542	890,000,000
10/19/21 due 11/3/21 (Collateralized by U.S. Treasury Obligations valued at $547,325,452, 0.00% - 6.50%, 4/14/22 - 5/15/50)	536,011,167	536,000,000
10/20/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,004,067,583, 0.00% - 6.50%, 1/31/22 - 2/15/51)	984,020,500	984,000,000
10/21/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $711,516,441, 0.00% - 6.50%, 11/16/21 - 11/15/50)	697,014,521	697,000,000
10/22/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,458,953,501, 0.00% - 6.50%, 11/4/21 - 2/15/51)	1,428,033,717	1,428,000,000
10/25/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $592,953,314, 0.00% - 7.25%, 11/4/21 - 5/15/50)	580,012,083	580,000,000
10/26/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,049,178,708, 0.09% - 6.38%, 7/31/22 - 8/15/51)	1,026,021,375	1,026,000,000
10/27/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $729,738,080, 0.09% - 6.50%, 2/28/22 - 2/15/48)	713,015,844	713,000,000
10/28/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,048,852,991, 0.00% - 7.13%, 12/23/21 - 5/15/50)	1,027,025,675	1,027,000,000
10/29/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $591,602,567, 0.00% - 6.50%, 11/4/21 - 8/15/51)	580,014,500	580,000,000
CIBC Bank U.S.A. at 0.06%, dated:
8/9/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $89,952,084, 0.00% - 3.13%, 7/14/22 - 2/15/50)	88,024,469	88,000,000
10/13/21 due 11/5/21
(Collateralized by U.S. Treasury Obligations valued at $181,883,579, 0.00% - 3.13%, 2/28/22 - 8/15/51)	178,025,019	178,000,000
(Collateralized by U.S. Treasury Obligations valued at $182,554,473, 0.13% - 3.63%, 4/30/22 - 8/15/51)	178,025,019	178,000,000
10/22/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $91,283,297, 0.13% - 2.63%, 2/28/22 - 2/15/50)	89,010,878	89,000,000
Citigroup Global Capital Markets, Inc. at 0.06%, dated 10/4/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $534,505,008, 0.00% - 1.25%, 11/30/21 - 7/31/23)	524,027,073	524,000,000
Commerz Markets LLC at 0.05%, dated:
10/26/21 due 11/2/21 (Collateralized by U.S. Treasury Obligations valued at $966,968,068, 0.08% - 2.75%, 4/30/23 - 5/15/30)	948,009,217	948,000,000
10/27/21 due 11/3/21 (Collateralized by U.S. Treasury Obligations valued at $725,230,972, 0.08% - 3.88%, 1/31/22 - 8/15/51)	711,006,913	711,000,000
10/28/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $363,122,081, 0.13% - 3.00%, 1/31/22 - 11/15/30)	356,003,461	356,000,000
10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $962,884,015, 0.08% - 2.75%, 1/31/22 - 2/15/30)	944,003,933	944,000,000
Credit AG at 0.05%, dated 10/29/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $188,490,807, 1.88% - 3.75%, 11/15/43 - 2/15/51)	183,001,779	183,000,000
Deutsche Bank AG, New York at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $364,692,925, 1.38% - 8.00%, 11/15/21 - 11/15/50)	356,001,483	356,000,000
DNB Bank ASA at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $145,860,698, 0.25% - 4.38%, 10/31/25 - 2/15/38)	143,000,596	143,000,000
Federal Reserve Bank of New York at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $79,911,332,989, 1.13% - 6.00%, 1/31/23 - 11/15/50)	79,911,332,963	79,911,000,000
Fixed Income Clearing Corp. - BNYM at 0.06%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $326,400,036, 0.13% - 0.38%, 7/15/23 - 1/15/31)	320,001,467	320,000,000
Fixed Income Clearing Corp.- Morgan Stanley & CO LLC at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $728,403,904, 2.38% - 2.88%, 11/30/23 - 8/15/24)	714,002,975	714,000,000
ING Financial Markets LLC at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $291,838,299, 0.00%, 11/4/21)	286,001,192	286,000,000
J.P. Morgan Securities, LLC at 0.05%, dated 10/29/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $358,022,265, 0.00%, 9/8/22)	351,003,413	351,000,000
Lloyds Bank Corp. Markets PLC at 0.07%, dated:
9/8/21 due 1/10/22 (Collateralized by U.S. Treasury Obligations valued at $182,543,227, 0.13% - 2.25%, 7/31/22 - 5/15/41)	179,043,159	179,000,000
9/21/21 due 1/21/22 (Collateralized by U.S. Treasury Obligations valued at $182,543,896, 0.13% - 1.13%, 7/31/22 - 8/15/40)	179,042,463	179,000,000
9/22/21 due 1/24/22 (Collateralized by U.S. Treasury Obligations valued at $182,538,721, 0.13% - 2.25%, 7/31/22 - 5/15/41)	179,043,159	179,000,000
9/30/21 due 1/18/22 (Collateralized by U.S. Treasury Obligations valued at $139,707,508, 1.13% - 2.38%, 1/31/23 - 5/15/41)	137,029,303	137,000,000
10/6/21 due 1/6/22 (Collateralized by U.S. Treasury Obligations valued at $183,279,423, 1.88%, 2/15/51)	178,031,842	178,000,000
10/12/21 due:
1/13/22 (Collateralized by U.S. Treasury Obligations valued at $109,108,790, 1.63% - 2.25%, 5/15/31 - 5/15/41)	107,019,349	107,000,000
2/3/22 (Collateralized by U.S. Treasury Obligations valued at $109,108,790, 1.63% - 2.25%, 5/15/31 - 5/15/41)	107,023,718	107,000,000
10/14/21 due 2/14/22 (Collateralized by U.S. Treasury Obligations valued at $181,501,080, 1.75%, 8/15/41)	178,042,572	178,000,000
10/28/21 due 1/31/22 (Collateralized by U.S. Treasury Obligations valued at $181,505,950, 2.25% - 2.50%, 1/31/25 - 5/15/41)	178,032,881	178,000,000
Mizuho Bank, Ltd. at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $636,942,133, 2.38%, 5/15/29)	625,002,604	625,000,000
MUFG Securities EMEA PLC at:
0.05%, dated 10/29/21 due:
11/1/21 (Collateralized by U.S. Treasury Obligations valued at $1,821,406,727, 0.25% - 2.88%, 10/15/22 - 8/15/28)	1,786,007,442	1,786,000,000
11/5/21 (Collateralized by U.S. Treasury Obligations valued at $411,952,033, 0.50% - 2.88%, 4/30/24 - 5/15/41)	404,006,733	404,000,000
0.06%, dated 10/5/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $166,221,973, 0.75% - 2.25%, 5/31/23 - 5/15/41)	163,008,467	163,000,000
Natixis SA at:
0.06%, dated:
8/16/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $89,772,035, 0.00% - 4.50%, 11/4/21 - 2/15/51)	88,013,493	88,000,000
8/19/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $544,767,985, 0.00% - 4.50%, 11/4/21 - 2/15/51)	534,075,057	534,000,000
0.07%, dated 8/17/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $181,128,289, 0.00% - 3.13%, 11/9/21 - 2/15/51)	177,563,506	177,500,000
Norinchukin Bank at 0.08%, dated:
8/12/21 due 11/10/21 (Collateralized by U.S. Treasury Obligations valued at $180,571,394, 1.50% - 6.75%, 6/30/25 - 5/15/27)	177,035,400	177,000,000
8/18/21 due 11/16/21 (Collateralized by U.S. Treasury Obligations valued at $180,568,948, 1.50% - 6.75%, 6/30/25 - 5/15/27)	177,035,400	177,000,000
8/19/21 due 11/17/21 (Collateralized by U.S. Treasury Obligations valued at $144,862,892, 1.50% - 6.75%, 6/30/25 - 5/15/27)	142,028,400	142,000,000
8/23/21 due 11/19/21 (Collateralized by U.S. Treasury Obligations valued at $263,199,227, 1.50% - 6.75%, 6/30/25 - 5/15/27)	258,050,453	258,000,000
8/24/21 due 11/22/21 (Collateralized by U.S. Treasury Obligations valued at $181,586,670, 1.50% - 6.75%, 6/30/25 - 5/15/27)	178,035,600	178,000,000
9/1/21 due 12/1/21 (Collateralized by U.S. Treasury Obligations valued at $90,791,770, 1.50% - 6.75%, 6/30/25 - 5/15/27)	89,017,998	89,000,000
10/12/21 due 1/11/22 (Collateralized by U.S. Treasury Obligations valued at $272,350,352, 1.50% - 6.75%, 6/30/25 - 5/15/27)	267,053,993	267,000,000
10/13/21 due 1/12/22 (Collateralized by U.S. Treasury Obligations valued at $217,267,828, 1.50% - 6.75%, 6/30/25 - 5/15/27)	213,043,073	213,000,000
10/14/21 due 1/14/22 (Collateralized by U.S. Treasury Obligations valued at $180,546,116, 1.50% - 6.75%, 6/30/25 - 5/15/27)	177,036,187	177,000,000
RBC Dominion Securities at:
0.05%, dated 9/16/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $366,615,301, 0.00% - 6.13%, 11/30/21 - 2/15/51)	358,044,750	358,000,000
0.06%, dated:
10/15/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $363,813,524, 0.00% - 6.13%, 11/30/21 - 5/15/51)	356,051,669	356,000,000
10/22/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $364,739,632, 0.00% - 6.50%, 11/30/21 - 5/15/51)	357,051,815	357,000,000
10/25/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $368,739,923, 1.25% - 2.75%, 5/31/28 - 8/15/47)	358,050,866	358,000,000
10/26/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $366,838,411, 0.13% - 6.13%, 11/30/21 - 2/15/47)	358,050,866	358,000,000
10/27/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $364,142,792, 0.00% - 3.00%, 12/15/21 - 8/15/47)	357,046,906	357,000,000
10/28/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $364,341,014, 0.00% - 2.75%, 1/20/22 - 5/15/51)	357,050,178	357,000,000
10/29/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $364,141,772, 0.00% - 3.13%, 11/30/21 - 11/15/47)	357,051,269	357,000,000
Royal Bank of Canada at:
0.05%, dated:
8/24/21 due 11/5/21
(Collateralized by U.S. Treasury Obligations valued at $163,215,713, 2.00% - 2.63%, 2/15/22 - 3/31/25)	160,022,222	160,000,000
(Collateralized by U.S. Treasury Obligations valued at $184,637,787, 1.63% - 2.50%, 2/15/22 - 2/15/25)	181,025,139	181,000,000
8/25/21 due 11/5/21
(Collateralized by U.S. Treasury Obligations valued at $163,215,481, 1.63% - 2.63%, 2/15/22 - 3/31/25)	160,022,222	160,000,000
(Collateralized by U.S. Treasury Obligations valued at $184,637,458, 1.63% - 2.50%, 2/15/22 - 8/15/25)	181,025,139	181,000,000
0.06%, dated 10/28/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $81,600,602, 2.00% - 2.50%, 8/15/23 - 8/15/25)	80,011,122	80,000,000
SMBC Nikko Securities America, Inc. at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $788,963,006, 0.50% - 5.38%, 2/15/25 - 5/15/50)	770,003,208	770,000,000
Societe Generale at 0.05%, dated 10/28/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $358,511,784, 0.00% - 8.00%, 11/4/21 - 5/15/51)	350,003,403	350,000,000
TD Securities (U.S.A.) at 0.05%, dated 10/29/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $177,480,824, 0.38% - 1.75%, 11/30/21 - 11/30/24)	174,000,725	174,000,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $109,363,500,000)		109,363,500,000
TOTAL INVESTMENT IN SECURITIES - 100.0%
(Cost $233,752,859,620)		233,752,859,620
NET OTHER ASSETS (LIABILITIES) - (0.1)%		(159,121,578)
NET ASSETS - 99.9%		$233,593,738,042

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) 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
$14,071,315,000 due 11/01/21 at 0.05%
BNY Mellon Capital Markets LLC	$979,551,000
Bank Of America, N.A.	1,255,019,000
Bank of America Securities, Inc.	1,394,466,000
Citigroup Global Markets, Inc.	522,925,000
Credit Agricole CIB New York Branch	729,260,000
Credit Suisse AG /New York NY	62,829,000
HSBC Securities (USA), Inc.	156,877,000
ING Financial Markets LLC	70,683,000
Mitsubishi UFJ Securities Co., Ltd	718,263,000
Mizuho Securities USA, Inc.	87,154,000
Nomura Securities International	2,053,351,000
RBC Dominion Securities, Inc.	174,308,000
Societe Generale	348,617,000
Sumitomo Mitsu Banking Corp. NY	3,391,451,000
Sumitomo Mitsui Banking Corp.	2,126,561,000
	$14,071,315,000
$52,000,000 due 11/01/21 at 0.05%
Bank of America Securities, Inc.	52,000,000
	$52,000,000

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

Financial Statements

Statement of Assets and Liabilities

		October 31, 2021 (Unaudited)
Assets
Investment in securities, at value (including repurchase agreements of $136,771,736,250) — See accompanying schedule: Unaffiliated issuers (cost $233,752,859,620)		$233,752,859,620
Cash		543
Receivable for investments sold		6,263,255,898
Receivable for fund shares sold		1,211,533,354
Interest receivable		176,562,089
Prepaid expenses		293,072
Receivable from investment adviser for expense reductions		51,629
Other receivables		1,660,175
Total assets		241,406,216,380
Liabilities
Payable for investments purchased	$6,930,852,567
Payable for fund shares redeemed	867,965,911
Distributions payable	219,087
Accrued management fee	9,988,596
Distribution and service plan fees payable	1,660
Other affiliated payables	449,573
Other payables and accrued expenses	3,000,944
Total liabilities		7,812,478,338
Net Assets		$233,593,738,042
Net Assets consist of:
Paid in capital		$233,593,512,555
Total accumulated earnings (loss)		225,487
Net Assets		$233,593,738,042
Net Asset Value and Maximum Offering Price
Capital Reserves Class:
Net Asset Value, offering price and redemption price per share ($7,405,561,147 ÷ 7,403,390,943 shares)		$1.00
Daily Money Class:
Net Asset Value, offering price and redemption price per share ($7,500,943,741 ÷ 7,498,962,317 shares)		$1.00
Advisor M Class:
Net Asset Value, offering price and redemption price per share ($126,836,693 ÷ 126,839,280 shares)		$1.00
Fidelity Government Money Market Fund:
Net Asset Value, offering price and redemption price per share ($212,367,136,653 ÷ 212,362,786,258 shares)		$1.00
Premium Class:
Net Asset Value, offering price and redemption price per share ($4,437,578,040 ÷ 4,436,451,000 shares)		$1.00
Class K6:
Net Asset Value, offering price and redemption price per share ($1,755,681,768 ÷ 1,755,703,872 shares)		$1.00

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

Statement of Operations

		Six months ended October 31, 2021 (Unaudited)
Investment Income
Interest		77,111,780
Expenses
Management fee	$282,002,630
Transfer agent fees	186,884,800
Distribution and service plan fees	28,111,727
Accounting fees and expenses	2,622,720
Custodian fees and expenses	567,022
Independent trustees' fees and expenses	338,487
Registration fees	4,701,176
Audit	23,913
Legal	104,739
Miscellaneous	340,969
Total expenses before reductions	505,698,183
Expense reductions	(439,901,957)
Total expenses after reductions		65,796,226
Net investment income (loss)		11,315,554
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		112,943
Total net realized gain (loss)		112,943
Net increase in net assets resulting from operations		$11,428,497

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

Statement of Changes in Net Assets

	Six months ended October 31, 2021 (Unaudited)	Year ended April 30, 2021
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$11,315,554	$20,884,477
Net realized gain (loss)	112,943	229,324
Net increase in net assets resulting from operations	11,428,497	21,113,801
Distributions to shareholders	(11,357,177)	(20,874,874)
Share transactions - net increase (decrease)	12,083,872,273	33,214,705,842
Total increase (decrease) in net assets	12,083,943,593	33,214,944,769
Net Assets
Beginning of period	221,509,794,449	188,294,849,680
End of period	$233,593,738,042	$221,509,794,449

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

Financial Highlights

Fidelity Government Money Market Fund Capital Reserves Class

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.009	.012	.003	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.009	.012	.003	–^A
Distributions from net investment income	–^A	–^A	(.009)	(.012)	(.003)	–^A
Total distributions	–^A	–^A	(.009)	(.012)	(.003)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.01%	.94%	1.26%	.27%	.01%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.95%^F	.96%	.97%	.96%	.96%	.97%
Expenses net of fee waivers, if any	.06%^F	.15%	.89%	.95%	.93%	.53%
Expenses net of all reductions	.06%^F	.15%	.89%	.95%	.93%	.53%
Net investment income (loss)	.01%^F	.01%	.87%	1.26%	.26%	.02%
Supplemental Data
Net assets, end of period (000 omitted)	$7,405,561	$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 for periods of less than one year are not annualized.

^C 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.

Fidelity Government Money Market Fund Daily Money Class

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.012	.015	.005	–^A
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.012	.015	.005	–^A
Distributions from net investment income	–^A	–^A	(.012)	(.015)	(.005)	–^A
Total distributions	–^A	–^A	(.012)	(.015)	(.005)	–^A
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.01%	1.16%	1.51%	.50%	.02%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.70%^F	.71%	.72%	.71%	.71%	.72%
Expenses net of fee waivers, if any	.06%^F	.15%	.67%	.70%	.70%	.52%
Expenses net of all reductions	.06%^F	.15%	.67%	.70%	.70%	.52%
Net investment income (loss)	.01%^F	.01%	1.08%	1.51%	.49%	.03%
Supplemental Data
Net assets, end of period (000 omitted)	$7,500,944	$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 for periods of less than one year are not annualized.

^C 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.

Fidelity Government Money Market Fund Advisor M Class

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	2021	2020	2019	2018 ^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)	–^B	–^B	.012	.015	.005
Net realized and unrealized gain (loss)^B	–	–	–	–	–
Total from investment operations	–^B	–^B	.012	.015	.005
Distributions from net investment income	–^B	–^B	(.012)	(.015)	(.005)
Total distributions	–^B	–^B	(.012)	(.015)	(.005)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.01%	.01%	1.17%	1.52%	.48%
Ratios to Average Net Assets^E,^F
Expenses before reductions	.70%^G	.71%	.72%	.71%	.72%^G
Expenses net of fee waivers, if any	.06%^G	.15%	.65%	.70%	.70%^G
Expenses net of all reductions	.06%^G	.15%	.64%	.69%	.69%^G
Net investment income (loss)	.01%^G	.01%	1.12%	1.53%	.71%^G
Supplemental Data
Net assets, end of period (000 omitted)	$126,837	$124,205	$126,269	$50,630	$29,889

^A For the period July 6, 2017 (commencement of sale of shares) through 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 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.

^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 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.

^G Annualized

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

Fidelity Government Money Market Fund

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.014	.018	.008	.001
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.014	.018	.008	.001
Distributions from net investment income	–^A	–^A	(.014)	(.018)	(.008)	(.001)
Total distributions	–^A	–^A	(.014)	(.018)	(.008)	(.001)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.01%	1.42%	1.79%	.78%	.12%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.42%^F	.42%	.42%	.42%	.42%	.42%
Expenses net of fee waivers, if any	.06%^F	.15%	.42%	.42%	.42%	.42%
Expenses net of all reductions	.06%^F	.15%	.42%	.42%	.42%	.42%
Net investment income (loss)	.01%^F	.01%	1.33%	1.79%	.81%	.14%
Supplemental Data
Net assets, end of period (000 omitted)	$212,367,137	$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 for periods of less than one year are not annualized.

^C 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.

Fidelity Government Money Market Fund Premium Class

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^A	–^A	.015	.019	.009	.002
Net realized and unrealized gain (loss)^A	–	–	–	–	–	–
Total from investment operations	–^A	–^A	.015	.019	.009	.002
Distributions from net investment income	–^A	–^A	(.015)	(.019)	(.009)	(.002)
Total distributions	–^A	–^A	(.015)	(.019)	(.009)	(.002)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^B,^C	.01%	.01%	1.52%	1.90%	.89%	.22%
Ratios to Average Net Assets^D,^E
Expenses before reductions	.35%^F	.36%	.37%	.36%	.36%	.37%
Expenses net of fee waivers, if any	.06%^F	.15%	.32%	.32%	.32%	.32%
Expenses net of all reductions	.06%^F	.15%	.32%	.32%	.32%	.32%
Net investment income (loss)	.01%^F	- %^G	1.43%	1.89%	.89%	.24%
Supplemental Data
Net assets, end of period (000 omitted)	$4,437,578	$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 for periods of less than one year are not annualized.

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

^F Annualized

^G Amount represents less than .005%.

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

Fidelity Government Money Market Fund Class K6

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	2021	2020	2019	2018 ^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)	–^B	–^B	.016	.019	.003
Net realized and unrealized gain (loss)^B	–	–	–	–	–
Total from investment operations	–^B	–^B	.016	.019	.003
Distributions from net investment income	–^B	–^B	(.016)	(.019)	(.003)
Total distributions	–^B	–^B	(.016)	(.019)	(.003)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.01%	.01%	1.59%	1.97%	.34%
Ratios to Average Net Assets^E,^F
Expenses before reductions	.27%^G	.27%	.28%	.27%	.27%^G
Expenses net of fee waivers, if any	.06%^G	.14%	.25%	.25%	.25%^G
Expenses net of all reductions	.06%^G	.14%	.25%	.25%	.25%^G
Net investment income (loss)	.01%^G	.01%	1.50%	1.96%	1.47%^G
Supplemental Data
Net assets, end of period (000 omitted)	$1,755,682	$1,660,582	$1,313,087	$404,595	$46,354

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

^G Annualized

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

Notes to Financial Statements (Unaudited)

For the period ended October 31, 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)

Fidelity Government Money Market Fund

$1,660,175

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.

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	$233,752,859,620

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%	$18,719,606	$15,604,354
Daily Money Class	-%	.25%	9,234,603	7,683,877
Advisor M Class	-%	.25%	157,518	131,102
			$28,111,727	$23,419,333

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	$1,382
Advisor M Class	$525

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^(a)
Capital Reserves Class	$7,487,843	.20
Daily Money Class	7,387,683	.20
Advisor M Class	126,015	.20
Fidelity Government Money Market Fund	169,515,490	.16
Premium Class	2,283,336	.10
Class K6	84,433	.01
	$186,884,800

(a) Annualized

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 ($)	Sales ($)	Realized Gain (Loss) ($)
Fidelity Government Money Market Fund	12,000,000	–	–

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%	$–
Daily Money Class	.70%	74,762
Advisor M Class	.70%	1,050
Premium Class	.32%	796,119
Class K6	.25%	130,579
		$1,002,510

Capital Reserves Class	$33,674,203
Daily Money Class	23,908,370
Advisor M Class	408,241
Fidelity Government Money Market Fund	373,222,986
Premium Class	6,044,406
Class K6	1,637,781

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. During the period, custodian credits reduced the Fund's expenses by $3,460.

5. Distributions to Shareholders.

Distributions to shareholders of each class were as follows:

	Six months ended October 31, 2021	Year ended April 30, 2021
Fidelity Government Money Market Fund
Distributions to shareholders
Capital Reserves Class	$376,856	$786,905
Daily Money Class	371,825	760,813
Advisor M Class	6,355	12,529
Fidelity Government Money Market Fund	10,286,852	18,527,218
Premium Class	230,171	574,686
Class K6	85,118	212,723
Total	$11,357,177	$20,874,874

6. Share Transactions.

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

	Shares	Shares	Dollars	Dollars
	Six months ended October 31, 2021	Year ended April 30, 2021	Six months ended October 31, 2021	Year ended April 30, 2021
Fidelity Government Money Market Fund
Capital Reserves Class
Shares sold	12,922,050,034	32,661,536,522	$12,922,050,034	$32,661,536,522
Reinvestment of distributions	230,979	499,618	230,979	499,618
Shares redeemed	(13,055,970,177)	(32,593,112,615)	(13,055,970,177)	(32,593,112,615)
Net increase (decrease)	(133,689,164)	68,923,525	$(133,689,164)	$68,923,525
Daily Money Class
Shares sold	12,804,365,785	24,900,123,722	$12,804,365,785	$24,900,123,722
Reinvestment of distributions	260,128	542,620	260,128	542,620
Shares redeemed	(12,659,948,803)	(25,379,435,893)	(12,659,948,803)	(25,379,435,893)
Net increase (decrease)	144,677,110	(478,769,551)	$144,677,110	$(478,769,551)
Advisor M Class
Shares sold	60,735,658	168,543,544	$60,735,658	$168,543,544
Reinvestment of distributions	6,221	12,309	6,221	12,309
Shares redeemed	(58,110,530)	(170,619,521)	(58,110,530)	(170,619,521)
Net increase (decrease)	2,631,349	(2,063,668)	$2,631,349	$(2,063,668)
Fidelity Government Money Market Fund
Shares sold	323,020,738,590	704,541,729,477	$323,020,738,584	$704,541,729,477
Reinvestment of distributions	9,349,385	17,041,021	9,349,385	17,041,021
Shares redeemed	(310,778,923,852)	(670,267,422,261)	(310,778,923,845)	(670,267,422,261)
Net increase (decrease)	12,251,164,123	34,291,348,237	$12,251,164,124	$34,291,348,237
Premium Class
Shares sold	869,228,170	2,950,419,613	$869,228,168	$2,950,419,613
Reinvestment of distributions	220,233	545,983	220,233	545,983
Shares redeemed	(1,145,460,189)	(3,963,201,241)	(1,145,460,188)	(3,963,201,241)
Net increase (decrease)	(276,011,786)	(1,012,235,645)	$(276,011,787)	$(1,012,235,645)
Class K6
Shares sold	626,009,382	1,666,993,981	$626,009,382	$1,666,993,981
Reinvestment of distributions	85,069	212,723	85,069	212,723
Shares redeemed	(530,993,810)	(1,319,703,760)	(530,993,810)	(1,319,703,760)
Net increase (decrease)	95,100,641	347,502,944	$95,100,641	$347,502,944

7. Other.

8. Coronavirus (COVID-19) Pandemic.

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 (May 1, 2021 to October 31, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value May 1, 2021	Ending Account Value October 31, 2021	Expenses Paid During Period-^B May 1, 2021 to October 31, 2021
Fidelity Government Money Market Fund
Capital Reserves Class	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**
Daily Money Class	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**
Advisor M Class	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**
Fidelity Government Money Market Fund	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**
Premium Class	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**
Class K6	.06%
Actual		$1,000.00	$1,000.10	$.30**
Hypothetical-^C		$1,000.00	$1,024.90	$.31**

^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		$4.78
Hypothetical-^(b)		$4.84
Daily Money Class	.70%
Actual		$3.52
Hypothetical-^(b)		$3.57
Advisor M Class	.70%
Actual		$3.52
Hypothetical-^(b)		$3.57
Fidelity Government Money Market Fund	.42%
Actual		$2.12
Hypothetical-^(b)		$2.14
Premium Class	.32%
Actual		$1.61
Hypothetical-^(b)		$1.63
Class K6	.25%
Actual		$1.26
Hypothetical-^(b)		$1.28

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

(b) 5% return per year before expenses

Board Approval of Investment Advisory Contracts and Management Fees

Fidelity Government Money Market Fund

At its September 2021 meeting, the Board unanimously determined to renew the fund's Advisory Contracts. In reaching its determination, the Board considered all factors it believed relevant, including (i) the nature, extent, and quality of the services provided to the fund and its shareholders (including the investment performance of the fund); (ii) the competitiveness relative to peer funds of the fund's management fee and total expense ratio of a representative class (the retail class); (iii) the total costs of the services provided by and the profits realized by Fidelity from its relationships with the fund; and (iv) the extent to which, if any, economies of scale exist and are realized as the fund grows, and whether any economies of scale are appropriately shared with fund shareholders.

Nature, Extent, and Quality of Services Provided. The Board considered Fidelity's staffing as it relates to the fund, including the backgrounds of investment personnel of Fidelity, and also considered the fund's investment objective, strategies, and related investment philosophy. The Independent Trustees also had discussions with senior management of Fidelity's investment operations and investment groups. The Board considered the structure of the investment personnel compensation program and whether this structure provides appropriate incentives to act in the best interests of the fund. Additionally, the Board considered the portfolio managers' investments, if any, in the funds that they manage. The Board also considered the steps Fidelity had taken to ensure the continued provision of high quality services to the Fidelity funds during the COVID-19 pandemic, including the expansion of staff in client facing positions to maintain service levels in periods of high volumes and volatility.

Based on its review, the Board concluded that the nature, extent, and quality of services provided to the fund under the Advisory Contracts should continue to benefit the shareholders of the fund.

Management Fee. The Board considered two proprietary management fee comparisons for the 12-month periods shown in basis points (BP) in the chart below. The group of Lipper funds used by the Board for management fee comparisons is referred to below as the "Total Mapped Group" and is broader than the Lipper peer group used by the Board for performance comparisons. The Total Mapped Group comparison focuses on a fund's standing in terms of gross management fees before expense reimbursements or caps relative to the total universe of funds with comparable investment mandates, regardless of whether their management fee structures also are comparable. Funds with comparable investment mandates offer exposure to similar types of securities. Funds with comparable management fee structures have similar management fee contractual arrangements (e.g., flat rate charged for advisory services, all-inclusive fee rate, etc.). "TMG %" represents the percentage of funds in the Total Mapped Group that had management fees that were lower than the fund's. For example, a hypothetical TMG % of 20% would mean that 80% of the funds in the Total Mapped Group had higher, and 20% had lower, management fees than the fund. The fund's actual TMG %s and the number of funds in the Total Mapped Group are in the chart below. The "Asset-Sized Peer Group" (ASPG) comparison focuses on a fund's standing relative to a subset of non-Fidelity funds within the Total Mapped Group that are similar in size and management fee structure. For example, if a fund is in the first quartile of the ASPG, the fund's management fee ranks in the least expensive or lowest 25% of funds in the ASPG. The ASPG represents at least 15% of the funds in the Total Mapped Group with comparable asset size and management fee structures, subject to a minimum of 50 funds (or all funds in the Total Mapped Group if fewer than 50). Additional information, such as the ASPG quartile in which the fund's management fee rate ranked, is also included in the chart and was considered by the Board.

The Board noted that the fund's management fee rate ranked below the median of its Total Mapped Group and above the median of its ASPG for 2020. The Board also noted that, excluding waivers and reimbursements, the total expense ratio of the representative class of the fund ranked below median.

Based on its review, the Board concluded that the fund's management fee is fair and reasonable in light of the services that the fund receives and the other factors considered.

Total Expense Ratio. In its review of the total expense ratio of the representative class (the retail class) of the fund, the Board considered the fund's management fee rate as well as other fund or class expenses, as applicable, such as transfer agent fees, pricing and bookkeeping fees, fund-paid 12b-1 fees, and custodial, legal, and audit fees. The Board also noted that Fidelity may agree to waive fees or reimburse expenses from time to time, and the extent to which, if any, it has done so for the fund. The fund's representative class is compared to those funds and classes in the Total Mapped Group (used by the Board for management fee comparisons) that have a similar sales load structure. The Board also considered a total expense ASPG comparison, which focuses on the total expenses of the representative class relative to a subset of non-Fidelity funds within the similar sales load structure group. The total expense ASPG is limited to 15 larger and 15 smaller classes of different funds, where possible. The total expense ASPG comparison excludes performance adjustments and fund-paid 12b-1 fees to eliminate variability in expenses relating to these items.

The Board noted that the total expense ratio of the retail class ranked below the similar sales load structure group competitive median for 2020 and below the ASPG competitive median for 2020.

The Board further considered that current contractual arrangements for the fund oblige FMR to pay all "class-level" expenses of the retail class of the fund to the extent necessary to limit total operating expenses, with certain exceptions, to 0.42%. These contractual arrangements may not be amended to increase the fees or expenses payable except by a vote of a majority of the Board and by a vote of a majority of the outstanding voting securities of the class. The Board further considered that FMR has contractually agreed to reimburse Capital Reserves Class, Daily Money Class, Class M, Class K6, and Premium Class of the fund to the extent that total operating expenses, with certain exceptions, as a percentage of their respective average net assets, exceed 0.95%, 0.70%, 0.70%, 0.25%, and 0.32% through August 31, 2022.

Economies of Scale. The Board considered whether there have been economies of scale in respect of the management of the Fidelity funds, whether the Fidelity funds (including the fund) have appropriately benefited from any such economies of scale, and whether there is potential for realization of any further economies of scale. The Board considered the extent to which the fund will benefit from economies of scale as assets grow through increased services to the fund, through waivers or reimbursements, or through fee or expense ratio reductions. The Board recognized that, due to the fund's current contractual arrangements, the expense ratio of the retail class will not decline if the class's operating costs decrease as assets grow, or rise as assets decrease. The Board also noted that a committee (the Economies of Scale Committee) created by it and the boards of other Fidelity funds periodically analyzes whether Fidelity attains economies of scale in respect of the management and servicing of the Fidelity funds, whether the Fidelity funds have appropriately benefited from such economies of scale, and whether there is potential for realization of any further economies of scale.

The Board concluded, taking into account the analysis of the Economies of Scale Committee, that economies of scale, if any, are being appropriately shared between fund shareholders and Fidelity.

Fidelity Investments

SPU-SANN-1221
1.538283.124

Fidelity Flex® Funds

Fidelity Flex® Government Money Market Fund

Semi-Annual Report

October 31, 2021

Contents

Note to Shareholders
Investment Summary/Performance
Schedule of Investments
Financial Statements
Notes to Financial Statements
Shareholder Expense Example
Board Approval of Investment Advisory Contracts and Management Fees

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 October 31, 2021

Days	% of fund's investments 10/31/21
1 - 7	38.0
8 - 30	17.8
31 - 60	12.1
61 - 90	9.8
91 - 180	17.3
> 180	5.0

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 October 31, 2021
	U.S. Treasury Debt	40.0%
	U.S. Government Agency Debt	31.1%
	Repurchase Agreements	24.6%
	Net Other Assets (Liabilities)	4.3%

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

Current 7-Day Yields

	10/31/21
Fidelity Flex® Government Money Market Fund	0.07%

Schedule of Investments October 31, 2021 (Unaudited)

Showing Percentage of Net Assets

U.S. Treasury Debt - 40.0%
	Yield(a)	Principal Amount	Value
U.S. Treasury Obligations - 40.0%
U.S. Treasury Bills
11/18/21 to 4/28/22	0.05 to 0.12%	$16,200,000	$16,197,799
U.S. Treasury Notes
11/15/21 to 7/31/23	0.04 to 0.21 (b)	24,300,000	24,368,716
TOTAL U.S. TREASURY DEBT
(Cost $40,566,515)			40,566,515

U.S. Government Agency Debt - 31.1%
Federal Agencies - 31.1%
Fannie Mae
1/11/22 to 7/29/22	0.06 to 0.25 (b)	2,950,000	2,970,620
Federal Farm Credit Bank
11/1/21 to 5/6/22	0.06 to 0.12 (b)	7,090,000	7,097,254
Federal Home Loan Bank
11/4/21 to 12/15/22	0.05 to 0.22 (b)	18,771,000	18,791,889
Freddie Mac
1/13/22 to 8/18/22	0.07 to 0.21 (b)	2,619,000	2,628,823
TOTAL U.S. GOVERNMENT AGENCY DEBT
(Cost $31,488,586)			31,488,586

U.S. Government Agency Repurchase Agreement - 8.3%
	Maturity Amount	Value
In a joint trading account at 0.06% dated 10/29/21 due 11/1/21 (Collateralized by U.S. Government Obligations) #	$397,002	$397,000
With:
BMO Harris Bank NA at 0.06%, dated:
9/1/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $1,020,096, 2.00% - 3.00%, 12/1/40 - 10/15/61)	1,000,139	1,000,000
9/13/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $1,020,077, 2.45% - 4.50%, 1/1/50 - 10/15/61)	1,000,139	1,000,000
Citibank NA at 0.06%, dated 10/26/21 due 11/2/21
(Collateralized by U.S. Treasury Obligations valued at $1,029,097, 0.00% - 2.88%, 4/30/23 - 8/15/28)	1,000,012	1,000,000
(Collateralized by U.S. Treasury Obligations valued at $1,020,059, 0.00% - 6.25%, 7/31/22 - 9/15/65)	1,000,012	1,000,000
Citigroup Global Capital Markets, Inc. at 0.06%, dated 10/26/21 due 11/2/21 (Collateralized by U.S. Government Obligations valued at $1,020,011, 2.50% - 3.00%, 10/20/51)	1,000,012	1,000,000
RBC Dominion Securities at:
0.05%, dated 9/10/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $1,020,121, 0.00% - 6.00%, 6/15/23 - 7/20/51)	1,000,126	1,000,000
0.06%, dated:
10/13/21 due 11/5/21 (Collateralized by U.S. Government Obligations valued at $1,020,092, 0.00% - 2.88%, 10/31/24 - 7/20/51)	1,000,153	1,000,000
10/14/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,085, 0.00% - 4.38%, 1/20/22 - 7/20/51)	1,000,153	1,000,000
TOTAL U.S. GOVERNMENT AGENCY REPURCHASE AGREEMENT
(Cost $8,397,000)		8,397,000

U.S. Treasury Repurchase Agreement - 16.3%
With:
BMO Harris Bank NA at 0.06%, dated 10/14/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,021,732, 0.00% - 3.88%, 11/18/21 - 2/15/51)	1,000,147	1,000,000
BNP Paribas, SA at 0.05%, dated:
10/15/21 due 11/1/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,084, 0.00% - 4.25%, 4/21/22 - 11/15/41)	1,000,024	1,000,000
10/18/21 due 11/2/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,027, 0.09% - 2.75%, 7/31/22 - 4/30/23)	1,000,021	1,000,000
10/19/21 due 11/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,055, 0.11% - 2.75%, 7/31/22 - 7/31/23)	1,000,021	1,000,000
10/20/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,017, 0.13% - 4.38%, 4/30/23 - 5/15/40)	1,000,021	1,000,000
10/21/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,078, 0.00% - 6.13%, 11/4/21 - 2/15/51)	1,000,021	1,000,000
10/22/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,066, 0.09% - 7.50%, 7/31/22 - 2/15/41)	1,000,024	1,000,000
10/25/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,011, 0.09% - 6.50%, 7/31/22 - 5/15/50)	1,000,021	1,000,000
10/26/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,042, 0.00% - 4.25%, 4/21/22 - 5/15/41)	1,000,021	1,000,000
Citigroup Global Capital Markets, Inc. at 0.06%, dated 10/4/21 due 11/4/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,083, 0.00%, 12/7/21 - 12/15/21)	1,000,052	1,000,000
Commerz Markets LLC at 0.05%, dated:
10/26/21 due 11/2/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,093, 0.75% - 1.00%, 4/30/26 - 7/31/28)	1,000,010	1,000,000
10/27/21 due 11/3/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,091, 0.63% - 0.75%, 4/30/26 - 7/31/26)	1,000,010	1,000,000
MUFG Securities EMEA PLC at 0.06%, dated 10/5/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,026,583, 1.38% - 2.25%, 8/31/23 - 5/15/41)	1,000,052	1,000,000
Natixis SA at:
0.06%, dated 8/16/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,363, 0.00% - 5.38%, 11/4/21 - 2/15/51)	1,000,153	1,000,000
0.07%, dated 8/17/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $510,122, 0.00% - 4.50%, 11/16/21 - 2/15/51)	500,179	500,000
RBC Dominion Securities at 0.06%, dated:
10/22/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,238, 0.00% - 3.00%, 11/30/21 - 5/15/50)	1,000,145	1,000,000
10/27/21 due 11/5/21 (Collateralized by U.S. Treasury Obligations valued at $1,020,089, 0.50% - 1.75%, 2/28/22 - 8/15/41)	1,000,131	1,000,000
TOTAL U.S. TREASURY REPURCHASE AGREEMENT
(Cost $16,500,000)		16,500,000
TOTAL INVESTMENT IN SECURITIES - 95.7%
(Cost $96,952,101)		96,952,101
NET OTHER ASSETS (LIABILITIES) - 4.3%		4,308,321
NET ASSETS - 100%		$101,260,422

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

Other Information

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

Repurchase Agreement / Counterparty	Value
$397,000 due 11/01/21 at 0.06%
BNY Mellon Capital Markets LLC	$397,000
	$397,000

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

Financial Statements

Statement of Assets and Liabilities

		October 31, 2021 (Unaudited)
Assets
Investment in securities, at value (including repurchase agreements of $24,897,000) — See accompanying schedule: Unaffiliated issuers (cost $96,952,101)		$96,952,101
Cash		316
Receivable for investments sold		1,301,156
Receivable for fund shares sold		9,292,043
Interest receivable		239,565
Total assets		107,785,181
Liabilities
Payable for investments purchased	$999,808
Payable for fund shares redeemed	5,523,078
Distributions payable	1,873
Total liabilities		6,524,759
Net Assets		$101,260,422
Net Assets consist of:
Paid in capital		$101,259,029
Total accumulated earnings (loss)		1,393
Net Assets		$101,260,422
Net Asset Value, offering price and redemption price per share ($101,260,422 ÷ 101,257,627 shares)		$1.00

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

Statement of Operations

		Six months ended October 31, 2021 (Unaudited)
Investment Income
Interest		$32,407
Expenses
Independent trustees' fees and expenses	$152
Total expenses before reductions	152
Expense reductions	(54)
Total expenses after reductions		98
Net investment income (loss)		32,309
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers		(98)
Total net realized gain (loss)		(98)
Net increase in net assets resulting from operations		$32,211

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

Statement of Changes in Net Assets

	Six months ended October 31, 2021 (Unaudited)	Year ended April 30, 2021
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$32,309	$103,798
Net realized gain (loss)	(98)	335
Net increase in net assets resulting from operations	32,211	104,133
Distributions to shareholders	(31,548)	(103,068)
Share transactions
Proceeds from sales of shares	2,136,271,072	3,017,435,302
Reinvestment of distributions	22,539	79,006
Cost of shares redeemed	(2,134,013,261)	(2,969,478,102)
Net increase (decrease) in net assets and shares resulting from share transactions	2,280,350	48,036,206
Total increase (decrease) in net assets	2,281,013	48,037,271
Net Assets
Beginning of period	98,979,409	50,942,138
End of period	$101,260,422	$98,979,409
Other Information
Shares
Sold	2,136,271,072	3,017,435,302
Issued in reinvestment of distributions	22,539	79,006
Redeemed	(2,134,013,261)	(2,969,478,102)
Net increase (decrease)	2,280,350	48,036,206

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

Financial Highlights

Fidelity Flex Government Money Market Fund

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	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	$1.00
Income from Investment Operations
Net investment income (loss)	–^B	.002	.018	.022	.012	.001
Net realized and unrealized gain (loss)	–^B	(.001)	–^B	–^B	–^B	–
Total from investment operations	–^B	.001	.018	.022	.012	.001
Distributions from net investment income	–^B	(.001)	(.018)	(.022)	(.012)	(.001)
Total distributions	–^B	(.001)	(.018)	(.022)	(.012)	(.001)
Net asset value, end of period	$1.00	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return^C,^D	.03%	.15%	1.81%	2.22%	1.23%	.12%
Ratios to Average Net Assets^E,^F
Expenses before reductions^G	- %^H	-%	-%	-%	-%	- %^H
Expenses net of fee waivers, if any^G	- %^H	-%	-%	-%	-%	- %^H
Expenses net of all reductions^G	- %^H	-%	-%	-%	-%	- %^H
Net investment income (loss)	.06%^H	.14%	1.64%	2.14%	1.39%	.78%^H
Supplemental Data
Net assets, end of period (000 omitted)	$101,260	$98,979	$50,942	$22,044	$53,685	$5,006

^A For the period March 8, 2017 (commencement of operations) through 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.

^G Amount represents less than .005%.

^H Annualized

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

Notes to Financial Statements (Unaudited)

For the period ended October 31, 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	$96,952,101

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 $54.

5. Other.

6. Coronavirus (COVID-19) Pandemic.

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 (May 1, 2021 to October 31, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value May 1, 2021	Ending Account Value October 31, 2021	Expenses Paid During Period-^B May 1, 2021 to October 31, 2021
Fidelity Flex Government Money Market Fund	- %-^C
Actual		$1,000.00	$1,000.30	$--^D
Hypothetical-^E		$1,000.00	$1,025.21	$--^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

Board Approval of Investment Advisory Contracts and Management Fees

Fidelity Flex Government Money Market Fund

At its September 2021 meeting, the Board unanimously determined to renew the fund's Advisory Contracts. In considering whether to renew the Advisory Contracts for the fund, the Board considered all factors it believed relevant and reached a determination, with the assistance of fund counsel and Independent Trustees' counsel and through the exercise of its business judgment, that the renewal of the Advisory Contracts was in the best interests of the fund and its shareholders and the fact that no fee is payable under the management contract was fair and reasonable.

Nature, Extent, and Quality of Services Provided. The Board considered Fidelity's staffing as it relates to the fund, including the backgrounds of investment personnel of Fidelity, and also considered the fund's investment objective, strategies, and related investment philosophy. The Independent Trustees also had discussions with senior management of Fidelity's investment operations and investment groups. The Board considered the structure of the investment personnel compensation program and whether this structure provides appropriate incentives to act in the best interests of the fund. Additionally, the Board considered the portfolio managers' investments, if any, in the funds that they manage. The Board also considered the steps Fidelity had taken to ensure the continued provision of high quality services to the Fidelity funds during the COVID-19 pandemic, including the expansion of staff in client facing positions to maintain service levels in periods of high volumes and volatility.

Shareholder and Administrative Services. The Board considered (i) the nature, extent, quality, and cost of advisory, administrative, and shareholder services performed by the Investment Advisers and their affiliates under the Advisory Contracts and under separate agreements covering transfer agency, pricing and bookkeeping, and securities lending services for the fund; (ii) the nature and extent of the supervision of third party service providers, principally custodians, subcustodians, and pricing vendors; and (iii) the resources devoted to, and the record of compliance with, the fund's compliance policies and procedures.

Investment Performance. The Board considered whether the fund has operated in accordance with its investment objective, as well as its record of compliance with its investment restrictions. The Board reviewed the fund's absolute investment performance, as well as the fund's relative investment performance. The Board did not consider performance to be a material factor in its decision to renew the fund's Advisory Contracts as the fund is not publicly offered as a stand-alone investment product. In this regard, the Board noted that the fund is available exclusively to certain fee-based accounts and advisor programs offered by Fidelity, including certain employer-sponsored plans and discretionary investment programs.

Based on its review, the Board concluded that the nature, extent, and quality of services provided to the fund under the Advisory Contracts should continue to benefit the shareholders of the fund.

Competitiveness of Management Fee and Total Expense Ratio. The Board noted that the fund is available exclusively through certain Fidelity fee-based accounts and advisory programs. The Board considered that the fund does not pay FMR a management fee for investment advisory services, but that FMR is indirectly compensated for its services out of Fidelity fee-based account and advisory program fees. The Board also noted that FMR or an affiliate undertakes to pay all operating expenses of the fund, except Independent Trustee fees and expenses, proxy and shareholder meeting expenses, interest, taxes, and extraordinary expenses (such as litigation expenses). The Board further noted that the fund pays its non-operating expenses, including brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable.

Based on its review, the Board considered that the fund does not pay a management fee and concluded that the fund's total expense ratio was reasonable in light of the services that the fund and its shareholders receive and the other factors considered.

Costs of the Services and Profitability. The Board considered the level of Fidelity's profits in respect of all the Fidelity funds.

The Board concluded that the costs of the services provided by and the profits realized by Fidelity in connection with the operation of the fund were not relevant to the renewal of the Advisory Contracts because the fund pays no advisory fees and FMR or an affiliate bears all expenses of the fund, with limited exceptions.

Economies of Scale. The Board concluded that because the fund pays no advisory fees and FMR or an affiliate bears all expenses of the fund with certain limited exceptions, the realization of economies of scale was not a material factor in the Board's decision to renew the fund's Advisory Contracts.

Fidelity Investments

ZGY-SANN-1221
1.9881598.104

Fidelity® Series Treasury Bill Index Fund

Semi-Annual Report

October 31, 2021

Contents

Note to Shareholders
Investment Summary
Schedule of Investments
Financial Statements
Notes to Financial Statements
Shareholder Expense Example
Board Approval of Investment Advisory Contracts and Management Fees

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

BLOOMBERG^® is a trademark and service mark of Bloomberg Finance L.P. and its affiliates (collectively “Bloomberg”). Bloomberg or Bloomberg’s licensors own all proprietary rights in the Bloomberg Indices. Neither Bloomberg nor Bloomberg’s licensors approves or endorses this material, or guarantees the accuracy or completeness of any information herein, or makes any warranty, express or implied, as to the results to be obtained therefrom and, to the maximum extent allowed by law, neither shall have any liability or responsibility for injury or damages arising in connection therewith.

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 (Unaudited)

Asset Allocation (% of fund's net assets)

As of October 31, 2021
	U.S. Government and U.S. Government Agency Obligations	100.0%

Schedule of Investments October 31, 2021 (Unaudited)

Showing Percentage of Net Assets

U.S. Government and Government Agency Obligations - 100.0%
	Principal Amount	Value
U.S. Treasury Obligations - 100.0%
U.S. Treasury Bills, yield at date of purchase 0.04% to 0.06% 2/3/22 to 4/28/22
(Cost $3,110,819,257)	3,111,385,000	3,110,690,329
TOTAL U.S. GOVERNMENT AND GOVERNMENT AGENCY OBLIGATIONS
(Cost $3,110,819,257)		3,110,690,329
	Shares	Value

Money Market Funds - 0.0%
Fidelity Cash Central Fund 0.06% (a)
(Cost $410,357)	410,275	410,357
TOTAL INVESTMENT IN SECURITIES - 100.0%
(Cost $3,111,229,614)		3,111,100,686
NET OTHER ASSETS (LIABILITIES) - 0.0%		668,996
NET ASSETS - 100%		$3,111,769,682

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 are available on the SEC's website or upon request.

Affiliated Central Funds

Fiscal year to date information regarding the Fund's investments in Fidelity Central Funds, including the ownership percentage, is presented below.

Fund	Value, beginning of period	Purchases	Sales Proceeds	Dividend Income	Realized Gain/Loss	Change in Unrealized appreciation (depreciation)	Value, end of period	% ownership, end of period
Fidelity Cash Central Fund 0.06%	$5,080,731	$123,291,986	$127,962,360	$1,528	$--	$--	$410,357	0.0%
Total	$5,080,731	$123,291,986	$127,962,360	$1,528	$--	$--	$410,357

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 October 31, 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	$3,110,690,329	$--	$3,110,690,329	$--
Money Market Funds	410,357	410,357	--	--
Total Investments in Securities:	$3,111,100,686	$410,357	$3,110,690,329	$--

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

Financial Statements

Statement of Assets and Liabilities

		October 31, 2021 (Unaudited)
Assets
Investment in securities, at value — See accompanying schedule: Unaffiliated issuers (cost $3,110,819,257)	$3,110,690,329
Fidelity Central Funds (cost $410,357)	410,357
Total Investment in Securities (cost $3,111,229,614)		$3,111,100,686
Cash		49,984
Receivable for investments sold		1,120,627,395
Receivable for fund shares sold		840,481
Distributions receivable from Fidelity Central Funds		159
Total assets		4,232,618,705
Liabilities
Payable for investments purchased	$924,877,121
Payable for fund shares redeemed	195,954,874
Other payables and accrued expenses	17,028
Total liabilities		1,120,849,023
Net Assets		$3,111,769,682
Net Assets consist of:
Paid in capital		$3,112,190,279
Total accumulated earnings (loss)		(420,597)
Net Assets		$3,111,769,682
Net Asset Value, offering price and redemption price per share ($3,111,769,682 ÷ 311,136,818 shares)		$10.00

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

Statement of Operations

		Six months ended October 31, 2021 (Unaudited)
Investment Income
Interest		$625,449
Income from Fidelity Central Funds		1,528
Total income		626,977
Expenses
Custodian fees and expenses	$17,203
Independent trustees' fees and expenses	5,374
Total expenses before reductions	22,577
Expense reductions	(2)
Total expenses after reductions		22,575
Net investment income (loss)		604,402
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment securities:
Unaffiliated issuers	(75,120)
Total net realized gain (loss)		(75,120)
Change in net unrealized appreciation (depreciation) on investment securities		(200,574)
Net gain (loss)		(275,694)
Net increase (decrease) in net assets resulting from operations		$328,708

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

Statement of Changes in Net Assets

	Six months ended October 31, 2021 (Unaudited)	Year ended April 30, 2021
Increase (Decrease) in Net Assets
Operations
Net investment income (loss)	$604,402	$3,004,074
Net realized gain (loss)	(75,120)	2,057,755
Change in net unrealized appreciation (depreciation)	(200,574)	(1,661,904)
Net increase (decrease) in net assets resulting from operations	328,708	3,399,925
Distributions to shareholders	(963,925)	(10,443,729)
Share transactions
Proceeds from sales of shares	636,553,695	1,648,546,820
Reinvestment of distributions	963,925	10,443,665
Cost of shares redeemed	(971,390,276)	(417,570,198)
Net increase (decrease) in net assets resulting from share transactions	(333,872,656)	1,241,420,287
Total increase (decrease) in net assets	(334,507,873)	1,234,376,483
Net Assets
Beginning of period	3,446,277,555	2,211,901,072
End of period	$3,111,769,682	$3,446,277,555
Other Information
Shares
Sold	63,655,369	164,748,562
Issued in reinvestment of distributions	96,393	1,044,006
Redeemed	(97,139,028)	(41,733,039)
Net increase (decrease)	(33,387,266)	124,059,529

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

Financial Highlights

Fidelity Series Treasury Bill Index Fund

	Six months ended (Unaudited) October 31,	Years endedApril 30,
	2021	2021	2020	2019 ^A
Selected Per–Share Data
Net asset value, beginning of period	$10.00	$10.03	$9.98	$10.00
Income from Investment Operations
Net investment income (loss)^B	.002	.011	.169	.166
Net realized and unrealized gain (loss)	.001^C	.002	.062	(.005)
Total from investment operations	.003	.013	.231	.161
Distributions from net investment income	(.002)	(.012)	(.175)	(.181)
Distributions from net realized gain	(.001)	(.031)	(.006)	–
Total distributions	(.003)	(.043)	(.181)	(.181)
Net asset value, end of period	$10.00	$10.00	$10.03	$9.98
Total Return^D,^E	.03%	.13%	2.34%	1.62%
Ratios to Average Net Assets^F,^G
Expenses before reductions^H	- %^I	-%	-%	- %^I
Expenses net of fee waivers, if any^H	- %^I	-%	-%	- %^I
Expenses net of all reductions^H	- %^I	-%	-%	- %^I
Net investment income (loss)	.03%^I	.11%	1.69%	2.36%^I
Supplemental Data
Net assets, end of period (000 omitted)	$3,111,770	$3,446,278	$2,211,901	$927,431

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

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

^C The amount shown for a share outstanding does not correspond with the aggregate net gain (loss) on investments for the period due to the timing of sales and repurchases of shares in relation to fluctuating market values of the investments of the Fund.

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

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

^F 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.

^G 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.

^H Amount represents less than .005%.

^I Annualized

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

Notes to Financial Statements (Unaudited)

For the period ended October 31, 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%

(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 contain the significant accounting policies (including investment valuation policies) of those funds, and 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 October 31, 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	$–
Gross unrealized depreciation	(129,007)
Net unrealized appreciation (depreciation)	$(129,007)
Tax cost	$3,111,229,693

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 commitment fees on the pro-rata portion of the line of credit are borne by the investment adviser. 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 $2.

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.

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 (May 1, 2021 to October 31, 2021).

Actual Expenses

Hypothetical Example for Comparison Purposes

	Annualized Expense Ratio-^A	Beginning Account Value May 1, 2021	Ending Account Value October 31, 2021	Expenses Paid During Period-^B May 1, 2021 to October 31, 2021
Fidelity Series Treasury Bill Index Fund	- %-^C
Actual		$1,000.00	$1,000.30	$--^D
Hypothetical-^E		$1,000.00	$1,025.21	$--^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

Board Approval of Investment Advisory Contracts and Management Fees

Fidelity Series Treasury Bill Index Fund

Nature, Extent, and Quality of Services Provided. The Board considered Fidelity's staffing as it relates to the fund, including the backgrounds of investment personnel of Fidelity, and also considered the fund's investment objective, strategies, and related investment philosophy. The Independent Trustees also had discussions with senior management of Fidelity's investment operations and investment groups. The Board considered the structure of the investment personnel compensation program and whether this structure provides appropriate incentives to act in the best interests of the fund. The Board also considered the steps Fidelity had taken to ensure the continued provision of high quality services to the Fidelity funds during the COVID-19 pandemic, including the expansion of staff in client facing positions to maintain service levels in periods of high volumes and volatility.

Administrative Services. The Board considered (i) the nature, extent, quality, and cost of advisory and administrative services performed by the Investment Advisers and their affiliates under the Advisory Contracts and under separate agreements covering transfer agency, pricing and bookkeeping, and securities lending services for the fund; (ii) the nature and extent of the supervision of third party service providers, principally custodians, subcustodians, and pricing vendors; and (iii) the resources devoted to, and the record of compliance with, the fund's compliance policies and procedures.

Investment Performance. The Board considered whether the fund has operated in accordance with its investment objective, as well as its record of compliance with its investment restrictions. The Board reviewed the fund's absolute investment performance, as well as the fund's relative investment performance. In this regard, the Board noted that the fund is designed to offer an investment option for other investment companies and 529 plans managed by Fidelity and ultimately to enhance the performance of those investment companies and 529 plans. The Board noted that there was a portfolio management change for the fund in October 2020.

Based on its review, the Board concluded that the nature, extent, and quality of services provided to the fund under the Advisory Contracts should continue to benefit the shareholders of the fund.

Competitiveness of Management Fee and Total Expense Ratio. The Board considered that the fund does not pay FMR a management fee for investment advisory services, but that FMR receives fees for providing services to funds that invest in the fund. The Board also noted that FMR or an affiliate undertakes to pay all operating expenses of the fund, except transfer agent fees, 12b-1 fees, Independent Trustee fees and expenses, custodian fees and expenses, proxy and shareholder meeting expenses, interest, taxes, and extraordinary expenses (such as litigation expenses). The Board further noted that the fund pays its non-operating expenses, including brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable.

The Board further considered that FMR has contractually agreed to reimburse the fund to the extent that total operating expenses, with certain exceptions, as a percentage of its average net assets, exceed 0.003% through August 31, 2024.

Costs of the Services and Profitability. The Board considered the level of Fidelity's profits in respect of all the Fidelity funds.

Fidelity Investments

XSB-SANN-1221
1.9891220.103

Item 2.

Code of Ethics

Not applicable.

Item 3.

Audit Committee Financial Expert

Not applicable.

Item 4.

Principal Accountant Fees and Services

Not applicable.

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 Fidelity Hereford Street 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 Fidelity Hereford Street Trust’s (the “Trust”) 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)	Not applicable.
(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:	December 21, 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:	December 21, 2021


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

Date:	December 21, 2021