Summary Prospectus by Investment Company - Form 497K

Fidelity Flex® Funds

Fund/Ticker

Fidelity Flex® Mid Cap Index Fund/FLAPX

Summary Prospectus

June 29, 2024

Before you invest, you may want to review the fund's prospectus, which contains more information about the fund and its risks. You can find the fund's prospectus, reports to shareholders, and other information about the fund (including the fund's SAI) online at www.fidelity.com/workplacedocuments. You can also get this information at no cost by calling 1-800-835-5095 or by sending an e-mail request to [email protected]. The fund's prospectus and SAI dated June 29, 2024 are incorporated herein by reference.

245 Summer Street, Boston, MA 02210

Fund Summary

Fund:

Fidelity Flex® Mid Cap Index Fund

Investment Objective

Fidelity Flex® Mid Cap Index Fund seeks to provide investment results that correspond to the total return of stocks of mid-capitalization United States companies.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. In addition to the fees and expenses described below, your broker may also require you to pay brokerage commissions on purchases and sales of the fund, which are not reflected in the table and example below.

Shareholder fees

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

AFidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent proxy and shareholder meeting expenses exceed 0.003% of the fund's average net assets. This arrangement will remain in effect through August 31, 2025. FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.

BThe fund is available only to certain fee-based accounts and advisory programs offered by Fidelity. Advisory account clients, retirement plans, plan sponsors and/or plan participants typically pay an advisory fee that generally covers investment advisory and administrative services.

This example helps compare the cost of investing in the fund with the cost of investing in other funds.

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. This example does not include any fees paid at the fee-based account or plan level. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 10% of the average value of its portfolio.

Principal Investment Strategies

Principal Investment Risks

Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.

The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole.

Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.

The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund, transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.

The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the fund's index or of the actual securities included in the index. This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund's performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities or lessen the impact of a market decline or a decline in the value of one or more issuers.

The value of securities of medium size, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.

Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.You could lose money by investing in the fund.

Performance

The following information is intended to help you understand the risks of investing in the fund.

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level.

Visit www.401k.com and log in or www.fidelity.com for more recent performance information.

Year-by-Year Returns

Average Annual Returns

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.

AFrom March 9, 2017.

Investment Adviser

Fidelity Management & Research Company LLC (FMR) (the Adviser) is the fund's manager. Geode Capital Management, LLC serves as a sub-adviser for the fund.

Portfolio Manager(s)

Louis Bottari (Senior Portfolio Manager) has managed the fund since 2017.

Peter Matthew (Senior Portfolio Manager) has managed the fund since 2017.

Navid Sohrabi (Senior Portfolio Manager) has managed the fund since 2019.

Robert Regan (Portfolio Manager) has managed the fund since 2017.

Payal Gupta (Portfolio Manager) has managed the fund since 2019.

Purchase and Sale of Shares

Shares are available only to certain fee-based accounts and advisory programs offered by Fidelity. Shares also may be available to certain broker-dealers that have entered into arrangements with Fidelity.

You may buy or sell shares in various ways:

Internet

Phone

Plan Accounts:

For Individual Accounts (investing through a retirement plan sponsor or other institution), refer to your plan materials or contact that institution directly.

For Retirement Plan Level Accounts:

Corporate Clients 1-800-962-1375

"Not for Profit" Clients 1-800-343-0860

All Other Accounts:

1-800-544-3455

Mail (Plan Accounts Only)

The price to buy one share is its net asset value per share (NAV). Shares will be bought at the NAV next calculated after an order is received in proper form.

The price to sell one share is its NAV. Shares will be sold at the NAV next calculated after an order is received in proper form.

The fund is open for business each day the New York Stock Exchange (NYSE) is open.

There is no purchase minimum for fund shares.

Tax Information

Distributions you receive from the fund are subject to federal income tax and generally will be taxed as ordinary income or capital gains, and may also be subject to state or local taxes, unless you are investing through a tax-advantaged retirement account (in which case you may be taxed later, upon withdrawal of your investment from such account).

Payments to Broker-Dealers and Other Financial Intermediaries

The Adviser, Fidelity Distributors Company LLC (FDC), and/or their affiliates may pay intermediaries, which may include banks, broker-dealers, retirement plan sponsors, administrators, or service-providers (who may be affiliated with the Adviser or FDC), for the sale of fund shares and related services. These payments may create a conflict of interest by influencing your intermediary and your investment professional to recommend the fund over another investment. Currently, the Board of Trustees of the fund has not authorized such payments for shares of the fund. Ask your investment professional or visit your intermediary's web site for more information.

Fidelity Distributors Company LLC (FDC) is a member of the Securities Investor Protection Corporation (SIPC). You may obtain information about SIPC, including the SIPC brochure, by visiting www.sipc.org or calling SIPC at 202-371-8300.

Fidelity, the Fidelity Investments Logo and all other Fidelity trademarks or service marks used herein are trademarks or service marks of FMR LLC. Any third-party marks that are used herein are trademarks or service marks of their respective owners. © 2024 FMR LLC. All rights reserved.