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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: 811-05986

T. Rowe Price Index Trust, Inc.

(Exact name of registrant as specified in charter)

100 East Pratt Street, Baltimore, MD 21202

(Address of principal executive offices)

David Oestreicher

100 East Pratt Street, Baltimore, MD 21202

(Name and address of agent for service)

Registrant’s telephone number, including area code: (410) 345-2000

Date of fiscal year end: December 31

Date of reporting period: June 30, 2017

The views and opinions in this report were current as of June 30, 2017. They are not guarantees of performance or investment results and should not be taken as investment advice. Investment decisions reflect a variety of factors, and the managers reserve the right to change their views about individual stocks, sectors, and the markets at any time. As a result, the views expressed should not be relied upon as a forecast of the fund’s future investment intent. The report is certified under the Sarbanes-Oxley Act, which requires mutual funds and other public companies to affirm that, to the best of their knowledge, the information in their financial reports is fairly and accurately stated in all material respects.

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The Mid-Cap Index Fund began operations in 2015 as a T. Rowe Price passively managed fund. The fund is not open for direct purchase by outside investors. It is intended to be used by T. Rowe Price’s asset allocation strategies as an additional investment option, as our actively managed mid-cap strategies are facing capacity constraints.

Mid-cap stocks produced positive results in the first six months of 2017. The Mid-Cap Index Fund returned 9.09% for the period ended June 30, 2017, versus 9.32% for the Russell Select Midcap Index. (Performance for the I Class will vary due to its differing fee structure.) Fund performance tends to slightly lag that of the benchmark because of the fund’s operating and management expenses.

U.S. stocks continued to surge in the first six months of the year. Strong corporate earnings growth in the first quarter helped to push the profits for S&P 500-listed companies higher, a welcome turnaround after five years of earnings declines that began in 2015. U.S. stocks continued their ascent into the second quarter, as the S&P 500 rose to record highs by June. The market generally shrugged off lackluster first-quarter economic growth, two interest rate increases from the Federal Reserve, President Donald Trump’s domestic political controversies, and Republicans’ failed attempts to repeal the Affordable Care Act.

In the mid-cap universe, growth stocks widely outperformed value stocks in the period. Much of the six-month performance stemmed from growth stocks’ greater exposure to noncyclical sectors, such as health care and information technology. However, over longer periods, the performance of mid-cap growth and value stocks has been more evenly matched. Mid-cap shares slightly lagged large-caps but decisively outpaced small-caps.

Nine of 11 sectors in the S&P 500 advanced, led by information technology and health care, which both returned more than 15%. Consumer discretionary and materials stocks were also notable solid performers. Energy and telecommunication services were the only two sectors to post negative returns.

The fund seeks to match the investment returns of mid-capitalization U.S. stocks by seeking to replicate the performance of the Russell Select Midcap Index, which also serves as the fund’s primary benchmark. The index, which was created for T. Rowe Price and will be administered by Russell Investment Group, consists of approximately 500 stocks and includes all stocks in the Russell 1000 Index, except for those also included in the S&P 500 Index. The fund seeks to employ a full-replication strategy, which involves investing substantially all of its assets in all of the stocks in the index and seeking to maintain holdings of each stock in proportion to its weight in the index.

In line with the allocations in the index, financials and information technology together account for approximately one-third of the fund’s investments. Consumer discretionary, industrials and business services, and real estate are also notable components at the sector level. Utilities and telecommunication services together compose less than 5% of assets.

Electric car maker Tesla was the largest component in the portfolio, and the stock performed well in the period. Semiconductor and processor manufacturer NXP Semiconductors and T-Mobile US were also among the largest positions at the end of the year, but their performances were weak. Social network Twitter performed on par with the average contribution of all mid-caps in the index. (Please refer to the fund’s portfolio of investments for a complete list of holdings and the amount each represents in the portfolio.)

Top stocks came from a variety of industries, including Internet service provider Liberty Broadband and restaurant company Yum China. Many of the strongest stocks were from the health care sector, which were in favor for many investors as the fear of a more punishing regulatory environment eased. Medical device maker Abiomed, biopharmaceutical company Alnylam Pharmaceuticals, and health care provider Acadia Healthcare all saw shares rise on optimism. Poor performers were also from a variety of industries, including retailer Urban Outfitters.

The outlook for the U.S. stock market is guardedly optimistic. The combination of U.S. policy instability and elevated valuations lends itself to heightened volatility and muted returns in the stock market in the near term. The first half of the year saw U.S. stocks trade at record levels, partly based on fiscal policies promised by President Trump, and any setback regarding their passage could dampen the market’s performance. Risks for the U.S. and global economic picture include monetary policy missteps and volatile energy prices, which remain vulnerable to a longer-term imbalance between supply and demand. U.S. economic growth is likely to remain steady but on course to remain below 2%. In addition, we expect interest rates to continue to rise but not on a preset course.

The committee chairman has day-to-day responsibility for managing the portfolio and works with committee members in developing and executing the fund’s investment program.

As with all stock mutual funds, the fund’s share price can fall because of weakness in the stock market, a particular industry, or specific holdings. Stock markets can decline for many reasons, including adverse political or economic developments, changes in investor psychology, or heavy institutional selling. The prospects for an industry or company may deteriorate because of a variety of factors, including disappointing earnings or changes in the competitive environment.

Investment-weighted median market capitalization: The investment weighted mid-point market capitalization (shares outstanding multiplied by current price) representing a typical security in a portfolio. An investment-weighted median represents the breakpoint where 50% of the values are above and 50% of the values are below based on portfolio weight.

Price-to-earnings (P/E) ratio: A valuation measure calculated by dividing the price of a stock by its reported earnings per share. The ratio is a measure of how much investors are willing to pay for the company’s earnings.

Projected earnings growth rate (IBES): A company’s expected earnings per share growth rate for a given time period based on the forecast from the Institutional Brokers’ Estimate System, which is commonly referred to as IBES.

Russell 1000 Index: An index that tracks the performance of the 1,000 largest companies in the Russell 3000 Index.

Russell Select Midcap Index: An unmanaged index that is designed to measure the performance of the mid-cap segment of the U.S. equity universe. It includes approximately 500 mid-cap U.S. securities based on market capitalization without consideration to a growth or value style.

S&P 500 Index: An unmanaged index that tracks the stocks of 500 primarily large-cap U.S. companies.

Note: Russell Investment Group is the source and owner of the trademarks, service marks, and copyrights related to the Russell indexes. Russell^® is a trademark of Russell Investment Group.

This chart shows the value of a hypothetical $10,000 investment in the fund over the past 10 fiscal year periods or since inception (for funds lacking 10-year records). The result is compared with benchmarks, which may include a broad-based market index and a peer group average or index. Market indexes do not include expenses, which are deducted from fund returns as well as mutual fund averages and indexes.

As a mutual fund shareholder, you may incur two types of costs: (1) transaction costs, such as redemption fees or sales loads, and (2) ongoing costs, including management fees, distribution and service (12b-1) fees, and other fund expenses. The following example is intended to help you understand your ongoing costs (in dollars) of investing in the 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 most recent six-month period and held for the entire period.

Please note that the fund has two share classes: The Investor Class charges no distribution and service (12b-1) fee, and the I Class shares are also available to institutionally oriented clients and impose no 12b-1 or administrative fee payment. Each share class is presented separately in the table.

Actual Expenses
The first line of the following table (Actual) provides information about actual account values and actual expenses. You may use the information on this line, together with your account balance, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number on the first line under the heading “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes
The information on the second line of the table (Hypothetical) is based on hypothetical account values and expenses derived from the fund’s actual expense ratio and an assumed 5% per year rate of return before expenses (not the fund’s actual return). You may compare the ongoing costs of investing in the fund with other funds by contrasting this 5% hypothetical example and the 5% hypothetical examples that appear in the shareholder reports of the other funds. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period.

Note: T. Rowe Price charges an account service fee that is not included in the accompanying table. The account service fee is charged on a quarterly basis, usually during the last week of a calendar quarter, and applies to accounts with balances below $10,000 on the day of the assessment. The fee is charged to accounts that fall below $10,000 for any reason, including market fluctuations, redemptions, or exchanges. When an account with less than $10,000 is closed either through redemption or exchange, the fee is charged and deducted from the proceeds. The fee applies to IRAs but not to retirement plans directly registered with T. Rowe Price Services or accounts maintained by intermediaries through NSCC^® Networking. If you are subject to the fee, keep it in mind when you are estimating the ongoing expenses of investing in the fund and when comparing the expenses of this fund with other funds.

You should also be aware that the expenses shown in the table highlight only your ongoing costs and do not reflect any transaction costs, such as redemption fees or sales loads. 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. To the extent a fund charges transaction costs, however, the total cost of owning that fund is higher.

T. Rowe Price Index Trust, Inc. (the corporation), is registered under the Investment Company Act of 1940 (the 1940 Act). The Mid-Cap Index Fund (the fund) is a diversified, open-end management investment company established by the corporation. The fund is available for investment only by mutual funds, college savings plans, and other institutional client accounts managed by T. Rowe Price Associates, Inc., or its affiliates and is not available for direct purchase by members of the public. The fund seeks to track the performance of a benchmark index that measures the investment return of mid-capitalization U.S. stocks. The fund has two classes of shares: the Mid-Cap Index Fund (Investor Class) and the Mid-Cap Index Fund–I Class (I Class). I Class shares generally are available only to investors meeting a $1,000,000 minimum investment or certain other criteria. Each class has exclusive voting rights on matters related solely to that class; separate voting rights on matters that relate to both classes; and, in all other respects, the same rights and obligations as the other class.

Basis of Preparation The fund is an investment company and follows accounting and reporting guidance in the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946 (ASC 946). The accompanying financial statements were prepared in accordance with accounting principles generally accepted in the United States of America (GAAP), including, but not limited to, ASC 946. GAAP requires the use of estimates made by management. Management believes that estimates and valuations are appropriate; however, actual results may differ from those estimates, and the valuations reflected in the accompanying financial statements may differ from the value ultimately realized upon sale or maturity.

Investment Transactions, Investment Income, and Distributions Income and expenses are recorded on the accrual basis. Dividends received from mutual fund investments are reflected as dividend income; capital gain distributions are reflected as realized gain/loss. Dividend income and capital gain distributions are recorded on the ex-dividend date. Income tax-related interest and penalties, if incurred, would be recorded as income tax expense. Investment transactions are accounted for on the trade date. Realized gains and losses are reported on the identified cost basis. Distributions from REITs are initially recorded as dividend income and, to the extent such represent a return of capital or capital gain for tax purposes, are reclassified when such information becomes available. Income distributions are declared and paid by each class annually. Distributions to shareholders are recorded on the ex-dividend date. A capital gain distribution may also be declared and paid by the fund annually.

Class Accounting Shareholder servicing, prospectus, and shareholder report expenses incurred by each class are charged directly to the class to which they relate. Expenses common to both classes, investment income, and realized and unrealized gains and losses are allocated to the classes based upon the relative daily net assets of each class.

New Accounting Guidance In October 2016, the Securities and Exchange Commission (SEC) issued a new rule, Investment Company Reporting Modernization, which, among other provisions, amends Regulation S-X to require standardized, enhanced disclosures, particularly related to derivatives, in investment company financial statements. Compliance with the guidance is effective for financial statements related to periods ending on or after August 1, 2017; adoption will have no effect on the fund’s net assets or results of operations.

The fund’s financial instruments are valued and each class’s net asset value (NAV) per share is computed at the close of the New York Stock Exchange (NYSE), normally 4 p.m. ET, each day the NYSE is open for business. However, the NAV per share may be calculated at a time other than the normal close of the NYSE if trading on the NYSE is restricted, if the NYSE closes earlier, or as may be permitted by the SEC.

Fair Value The fund’s financial instruments are reported at fair value, which GAAP defines as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The T. Rowe Price Valuation Committee (the Valuation Committee) is an internal committee that has been delegated certain responsibilities by the fund’s Board of Directors (the Board) to ensure that financial instruments are appropriately priced at fair value in accordance with GAAP and the 1940 Act. Subject to oversight by the Board, the Valuation Committee develops and oversees pricing-related policies and procedures and approves all fair value determinations. Specifically, the Valuation Committee establishes procedures to value securities; determines pricing techniques, sources, and persons eligible to effect fair value pricing actions; oversees the selection, services, and performance of pricing vendors; oversees valuation-related business continuity practices; and provides guidance on internal controls and valuation-related matters. The Valuation Committee reports to the Board and has representation from legal, portfolio management and trading, operations, risk management, and the fund’s treasurer.

Various valuation techniques and inputs are used to determine the fair value of financial instruments. GAAP establishes the following fair value hierarchy that categorizes the inputs used to measure fair value:

Level 1 – quoted prices (unadjusted) in active markets for identical financial instruments that the fund can access at the reporting date

Level 2 – inputs other than Level 1 quoted prices that are observable, either directly or indirectly (including, but not limited to, quoted prices for similar financial instruments in active markets, quoted prices for identical or similar financial instruments in inactive markets, interest rates and yield curves, implied volatilities, and credit spreads)

Observable inputs are developed using market data, such as publicly available information about actual events or transactions, and reflect the assumptions that market participants would use to price the financial instrument. Unobservable inputs are those for which market data are not available and are developed using the best information available about the assumptions that market participants would use to price the financial instrument. GAAP requires valuation techniques to maximize the use of relevant observable inputs and minimize the use of unobservable inputs. When multiple inputs are used to derive fair value, the financial instrument is assigned to the level within the fair value hierarchy based on the lowest-level input that is significant to the fair value of the financial instrument. Input levels are not necessarily an indication of the risk or liquidity associated with financial instruments at that level but rather the degree of judgment used in determining those values.

Valuation Techniques Equity securities listed or regularly traded on a securities exchange or in the over-the-counter (OTC) market are valued at the last quoted sale price or, for certain markets, the official closing price at the time the valuations are made. OTC Bulletin Board securities are valued at the mean of the closing bid and asked prices. A security that is listed or traded on more than one exchange is valued at the quotation on the exchange determined to be the primary market for such security. Listed securities not traded on a particular day are valued at the mean of the closing bid and asked prices. Actively traded equity securities listed on a domestic exchange generally are categorized in Level 1 of the fair value hierarchy. OTC Bulletin Board securities, certain preferred securities, and equity securities traded in inactive markets generally are categorized in Level 2 of the fair value hierarchy.

Investments in mutual funds are valued at the mutual fund’s closing NAV per share on the day of valuation and are categorized in Level 1 of the fair value hierarchy. Assets and liabilities other than financial instruments, including short-term receivables and payables, are carried at cost, or estimated realizable value, if less, which approximates fair value.

Thinly traded financial instruments and those for which the above valuation procedures are inappropriate or are deemed not to reflect fair value are stated at fair value as determined in good faith by the Valuation Committee. The objective of any fair value pricing determination is to arrive at a price that could reasonably be expected from a current sale. Financial instruments fair valued by the Valuation Committee are primarily private placements, restricted securities, warrants, rights, and other securities that are not publicly traded.

Subject to oversight by the Board, the Valuation Committee regularly makes good faith judgments to establish and adjust the fair valuations of certain securities as events occur and circumstances warrant. For instance, in determining the fair value of an equity investment with limited market activity, such as a private placement or a thinly traded public company stock, the Valuation Committee considers a variety of factors, which may include, but are not limited to, the issuer’s business prospects, its financial standing and performance, recent investment transactions in the issuer, new rounds of financing, negotiated transactions of significant size between other investors in the company, relevant market valuations of peer companies, strategic events affecting the company, market liquidity for the issuer, and general economic conditions and events. In consultation with the investment and pricing teams, the Valuation Committee will determine an appropriate valuation technique based on available information, which may include both observable and unobservable inputs. The Valuation Committee typically will afford greatest weight to actual prices in arm’s length transactions, to the extent they represent orderly transactions between market participants, transaction information can be reliably obtained, and prices are deemed representative of fair value. However, the Valuation Committee may also consider other valuation methods such as market-based valuation multiples; a discount or premium from market value of a similar, freely traded security of the same issuer; or some combination. Fair value determinations are reviewed on a regular basis and updated as information becomes available, including actual purchase and sale transactions of the issue. Because any fair value determination involves a significant amount of judgment, there is a degree of subjectivity inherent in such pricing decisions, and fair value prices determined by the Valuation Committee could differ from those of other market participants. Depending on the relative significance of unobservable inputs, including the valuation technique(s) used, fair valued securities may be categorized in Level 2 or 3 of the fair value hierarchy.

Valuation Inputs On June 30, 2017, all of the fund’s financial instruments were classified as Level 1, based on the inputs used to determine their fair values. There were no material transfers between Levels 1 and 2 during the six months ended June 30, 2017.

Consistent with its investment objective, the fund engages in the following practices to manage exposure to certain risks and/or to enhance performance. The investment objective, policies, program, and risk factors of the fund are described more fully in the fund’s prospectus and Statement of Additional Information.

Securities Lending The fund may lend its securities to approved brokers to earn additional income. Its securities lending activities are administered by a lending agent in accordance with a securities lending agreement. Security loans generally do not have stated maturity dates, and the fund may recall a security at any time. The fund receives collateral in the form of cash or U.S. government securities, valued at 102% to 105% of the value of the securities on loan. Collateral is maintained over the life of the loan in an amount not less than the value of loaned securities; any additional collateral required due to changes in security values is delivered to the fund the next business day. Cash collateral is invested by the lending agent(s) in accordance with investment guidelines approved by fund management. Additionally, the lending agent indemnifies the fund against losses resulting from borrower default. Although risk is mitigated by the collateral and indemnification, the fund could experience a delay in recovering its securities and a possible loss of income or value if the borrower fails to return the securities, collateral investments decline in value, and the lending agent fails to perform. Securities lending revenue consists of earnings on invested collateral and borrowing fees, net of any rebates to the borrower, compensation to the lending agent, and other administrative costs. In accordance with GAAP, investments made with cash collateral are reflected in the accompanying financial statements, but collateral received in the form of securities is not. At June 30, 2017, the value of loaned securities was $202,000; the value of cash collateral and related investments was $206,000.

Other Purchases and sales of portfolio securities other than short-term securities aggregated $1,166,000 and $1,124,000, respectively, for the six months ended June 30, 2017.

No provision for federal income taxes is required since the fund intends to continue to qualify as a regulated investment company under Subchapter M of the Internal Revenue Code and distribute to shareholders all of its taxable income and gains. Distributions determined in accordance with federal income tax regulations may differ in amount or character from net investment income and realized gains for financial reporting purposes. Financial reporting records are adjusted for permanent book/tax differences to reflect tax character but are not adjusted for temporary differences. The amount and character of tax-basis distributions and composition of net assets are finalized at fiscal year-end; accordingly, tax-basis balances have not been determined as of the date of this report.

At June 30, 2017, the cost of investments for federal income tax purposes was $5,305,000. Net unrealized gain aggregated $887,000 at period-end, of which $1,078,000 related to appreciated investments and $191,000 related to depreciated investments.

The fund is managed by T. Rowe Price Associates, Inc. (Price Associates), a wholly owned subsidiary of T. Rowe Price Group, Inc. (Price Group). The investment management agreement between the fund and Price Associates provides for an annual investment management fee equal to 0.12% of the fund’s average daily net assets. The fee is computed daily and paid monthly.

The Investor Class is subject to a contractual expense limitation through April 30, 2018. During the limitation period, Price Associates is required to waive its management fee or pay any expenses (excluding interest, expenses related to borrowings, taxes, brokerage, and other non-recurring expenses permitted by the investment management agreement) that would otherwise cause the class’s ratio of annualized total expenses to average net assets (expense ratio) to exceed its expense limitation of 0.32%. The class is required to repay Price Associates for expenses previously waived/paid to the extent the class’s net assets grow or expenses decline sufficiently to allow repayment without causing the class’s expense ratio to exceed its expense limitation in effect at the time of the waiver. However, no repayment will be made more than three years after the date of a payment or waiver. For the six months ended June 30, 2017, the Investor Class operated below its expense limitation.

The I Class is also subject to an operating expense limitation (I Class limit) pursuant to which Price Associates is contractually required to pay all operating expenses of the I Class, excluding management fees, interest, expenses related to borrowings, taxes, brokerage, and other non-recurring expenses permitted by the investment management agreement, to the extent such operating expenses, on an annualized basis, exceed 0.05% of average net assets. This agreement will continue until April 30, 2018, and may be renewed, revised, or revoked only with approval of the fund’s Board. The I Class is required to repay Price Associates for expenses previously paid to the extent the class’s net assets grow or expenses decline sufficiently to allow repayment without causing the class’s operating expenses to exceed the I Class limit in effect at the time of the waiver. However, no repayment will be made more than three years after the date of a payment or waiver.

Pursuant to these agreements, $111,000 of expenses were waived/paid by Price Associates during the six months ended June 30, 2017. Including these amounts, expenses previously waived/paid by Price Associates in the amount of $341,000 remain subject to repayment by the fund at June 30, 2017.

In addition, the fund has entered into service agreements with Price Associates and two wholly owned subsidiaries of Price Associates (collectively, Price). Price Associates provides certain accounting and administrative services to the fund. T. Rowe Price Services, Inc. provides shareholder and administrative services in its capacity as the fund’s transfer and dividend-disbursing agent. T. Rowe Price Retirement Plan Services, Inc. provides subaccounting and recordkeeping services for certain retirement accounts invested in the Investor Class and I Class. For the six months ended June 30, 2017, expenses incurred pursuant to these service agreements were $41,000 for Price Associates and less than $1,000 for T. Rowe Price Services, Inc. The total amount payable at period-end pursuant to these service agreements is reflected as Due to Affiliates in the accompanying financial statements.

The fund may invest in the T. Rowe Price Government Reserve Fund, the T. Rowe Price Treasury Reserve Fund, or the T. Rowe Price Short-Term Fund (collectively, the Price Reserve Funds), open-end management investment companies managed by Price Associates and considered affiliates of the fund. The Price Reserve Funds are offered as short-term investment options to mutual funds, trusts, and other accounts managed by Price Associates or its affiliates and are not available for direct purchase by members of the public. The Price Reserve Funds pay no investment management fees.

As of June 30, 2017, T. Rowe Price Group, Inc., or its wholly owned subsidiaries owned 475,000 shares of the Investor Class, representing 100% of the Investor Class’s net assets and 25,000 shares of the I Class, representing 100% of the I Class’s net assets.

The fund may participate in securities purchase and sale transactions with other funds or accounts advised by Price Associates (cross trades), in accordance with procedures adopted by the fund’s Board and Securities and Exchange Commission rules, which require, among other things, that such purchase and sale cross trades be effected at the independent current market price of the security. During the six months ended June 30, 2017, the fund had no purchases or sales cross trades with other funds or accounts advised by Price Associates.

A description of the policies and procedures used by T. Rowe Price funds and portfolios to determine how to vote proxies relating to portfolio securities is available in each fund’s Statement of Additional Information. You may request this document by calling 1-800-225-5132 or by accessing the SEC’s website, sec.gov.

The description of our proxy voting policies and procedures is also available on our corporate website. To access it, please visit the following Web page:

Scroll down to the section near the bottom of the page that says, “Proxy Voting Policies.” Click on the Proxy Voting Policies link in the shaded box.

Each fund’s most recent annual proxy voting record is available on our website and through the SEC’s website. To access it through T. Rowe Price, visit the website location shown above, and scroll down to the section near the bottom of the page that says, “Proxy Voting Records.” Click on the Proxy Voting Records link in the shaded box.

The fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission for the first and third quarters of each fiscal year on Form N-Q. The fund’s Form N-Q is available electronically on the SEC’s website (sec.gov); hard copies may be reviewed and copied at the SEC’s Public Reference Room, 100 F St. N.E., Washington, DC 20549. For more information on the Public Reference Room, call 1-800-SEC-0330.

Each year, the fund’s Board of Directors (Board) considers the continuation of the investment management agreement (Advisory Contract) between the fund and its investment advisor, T. Rowe Price Associates, Inc. (Advisor). In that regard, at an in-person meeting held on March 6–7, 2017 (Meeting), the Board, including a majority of the fund’s independent directors, approved the continuation of the fund’s Advisory Contract. At the Meeting, the Board considered the factors and reached the conclusions described below relating to the selection of the Advisor and the approval of the Advisory Contract. The independent directors were assisted in their evaluation of the Advisory Contract by independent legal counsel from whom they received separate legal advice and with whom they met separately.

In providing information to the Board, the Advisor was guided by a detailed set of requests for information submitted by independent legal counsel on behalf of the independent directors. In considering and approving the Advisory Contract, the Board considered the information it believed was relevant, including, but not limited to, the information discussed below. The Board considered not only the specific information presented in connection with the Meeting but also the knowledge gained over time through interaction with the Advisor about various topics. 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 T. Rowe Price funds’ advisory contracts, including performance and the services and support provided to the funds and their shareholders.

Services Provided by the Advisor
The Board considered the nature, quality, and extent of the services provided to the fund by the Advisor. These services included, but were not limited to, directing the fund’s investments in accordance with its investment program and the overall management of the fund’s portfolio, as well as a variety of related activities such as financial, investment operations, and administrative services; compliance; maintaining the fund’s records and registrations; and shareholder communications. The Board also reviewed the background and experience of the Advisor’s senior management team and investment personnel involved in the management of the fund, as well as the Advisor’s compliance record. The Board concluded that it was satisfied with the nature, quality, and extent of the services provided by the Advisor.

Investment Performance of the Fund
The Board took into account discussions with the Advisor and reports that it receives throughout the year relating to fund performance. On the basis of the Board’s ongoing review of investment results, and factoring in the fund’s relatively limited operating history, the Board concluded that the fund’s performance was satisfactory.

Costs, Benefits, Profits, and Economies of Scale
The Board reviewed detailed information regarding the revenues received by the Advisor under the Advisory Contract and other benefits that the Advisor (and its affiliates) may have realized from its relationship with the fund, including any research received under “soft dollar” agreements and commission-sharing arrangements with broker-dealers. The Board considered that the Advisor may receive some benefit from soft-dollar arrangements pursuant to which research is received from broker-dealers that execute the fund’s portfolio transactions. The Board received information on the estimated costs incurred and profits realized by the Advisor from managing the T. Rowe Price funds. While the Board did not review information regarding profits realized from managing the fund in particular because the fund had either not achieved sufficient portfolio asset size or not recognized sufficient revenues to produce meaningful profit margin percentages, the Board concluded that the Advisor’s profits were reasonable in light of the services provided to the T. Rowe Price funds.

The Board also considered whether the fund benefits under the fee levels set forth in the Advisory Contract from any economies of scale realized by the Advisor. Under the Advisory Contract, the fund pays a fee to the Advisor for investment management services based on the fund’s average daily net assets and the fund pays its own expenses of operations (subject to contractual expense limitations agreed to by the Advisor with respect to the Investor Class and I Class). The fund’s shareholders benefit from potential economies of scale through a decline in certain operating expenses as the fund grows in size and the fund has a contractual expense limitation in place to reduce the burden of higher operating costs to shareholders. The Board concluded that the advisory fee structure for the fund continued to be appropriate.

Fees and Expenses
The Board was provided with information regarding industry trends in management fees and expenses. Among other things, the Board reviewed data for peer groups that were compiled by Broadridge, which compared: (i) contractual management fees, total expenses, actual management fees, and non-management expenses of the fund with a group of competitor funds selected by Broadridge (Expense Group) and (ii) total expenses, actual management fees, and non-management expenses of the fund with a broader set of funds within the Lipper investment classification (Expense Universe). The Board considered the fund’s contractual management fee rate, actual management fee rate (which reflects the management fees actually received from the fund by the Advisor after any applicable waivers, reductions, or reimbursements), operating expenses, and total expenses (which reflect the net total expense ratio of the fund after any waivers, reductions, or reimbursements) in comparison with the information for the Broadridge peer groups. Broadridge generally constructed the peer groups by seeking the most comparable funds based on similar investment classifications and objectives, expense structure, asset size, and operating components and attributes and ranked funds into quintiles, with the first quintile representing the funds with the lowest relative expenses and the fifth quintile representing the funds with the highest relative expenses. The information provided to the Board indicated that the fund’s contractual management fee ranked in the first quintile (Expense Group), the fund’s actual management fee rate ranked in the first quintile (Expense Group and Expense Universe), and the fund’s total expenses ranked in the first quintile (Expense Group and Expense Universe).

The Board also reviewed the fee schedules for institutional accounts and private accounts with similar mandates that are advised or subadvised by the Advisor and its affiliates. Management provided the Board with information about the Advisor’s responsibilities and services provided to subadvisory and other institutional account clients, including information about how the requirements and economics of the institutional business are fundamentally different from those of the mutual fund business. The Board considered information showing that the Advisor’s mutual fund business is generally more complex from a business and compliance perspective than its institutional account business and considered various relevant factors, such as the broader scope of operations and oversight, more extensive shareholder communication infrastructure, greater asset flows, heightened business risks, and differences in applicable laws and regulations associated with the Advisor’s proprietary mutual fund business. In assessing the reasonableness of the fund’s management fee rate, the Board considered the differences in the nature of the services required for the Advisor to manage its mutual fund business versus managing a discrete pool of assets as a subadvisor to another institution’s mutual fund or for an institutional account and that the Advisor generally performs significant additional services and assumes greater risk in managing the fund and other T. Rowe Price funds than it does for institutional account clients.

On the basis of the information provided and the factors considered, the Board concluded that the fees paid by the fund under the Advisory Contract are reasonable.

Approval of the Advisory Contract
As noted, the Board approved the continuation of the Advisory Contract. No single factor was considered in isolation or to be determinative to the decision. Rather, the Board concluded, in light of a weighting and balancing of all factors considered, that it was in the best interests of the fund and its shareholders for the Board to approve the continuation of the Advisory Contract (including the fees to be charged for services thereunder).

A code of ethics, as defined in Item 2 of Form N-CSR, applicable to its principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions is filed as an exhibit to the registrant’s annual Form N-CSR. No substantive amendments were approved or waivers were granted to this code of ethics during the registrant’s most recent fiscal half-year.

(a) Not applicable. The complete schedule of investments is included in Item 1 of this Form N-CSR.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies.

Item 9. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.

(a) The registrant’s principal executive officer and principal financial officer have evaluated the registrant’s disclosure controls and procedures within 90 days of this filing and have concluded that the registrant’s disclosure controls and procedures were effective, as of that date, in ensuring that information required to be disclosed by the registrant in this Form N-CSR was recorded, processed, summarized, and reported timely.

(b) The registrant’s principal executive officer and principal financial officer are aware of no change in the registrant’s internal control over financial reporting that occurred during the registrant’s second fiscal quarter covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

(a)(1) The registrant’s code of ethics pursuant to Item 2 of Form N-CSR is filed with the registrant’s annual Form N-CSR.

(2) Separate certifications by the registrant's principal executive officer and principal financial officer, pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 and required by Rule 30a-2(a) under the Investment Company Act of 1940, are attached.

(3) Written solicitation to repurchase securities issued by closed-end companies: not applicable.

(b) A certification by the registrant's principal executive officer and principal financial officer, pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and required by Rule 30a-2(b) under the Investment Company Act of 1940, is attached.

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.

T. Rowe Price Index Trust, Inc.

	By	/s/ Edward C. Bernard
		Edward C. Bernard
		Principal Executive Officer

Date August 21, 2017

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/ Edward C. Bernard
		Edward C. Bernard
		Principal Executive Officer

Date August 21, 2017


	By	/s/ Catherine D. Mathews
		Catherine D. Mathews
		Principal Financial Officer

Date August 21, 2017