Summary Prospectus by Investment Company (Form 497K)

Fund/Ticker

Fidelity® Long-Term Treasury Bond Index Fund/FNBGX

Summary Prospectus

April 29, 2026

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 fundresearch.fidelity.com/prospectus/sec. You can also get this information at no cost by calling 1-800-FIDELITY or by sending an e-mail request to [email protected]. The fund's prospectus and SAI dated April 29, 2026 are incorporated herein by reference.

245 Summer Street, Boston, MA 02210

Fund Summary

Fund:

Fidelity® Long-Term Treasury Bond Index Fund

Investment Objective

Fidelity® Long-Term Treasury Bond Index Fund seeks a high level of current income.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions, which are not reflected in the tables and examples below.

Shareholder fees

(fees paid directly from your investment)

None

Annual Operating Expenses

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

Management fee	0.03%
Distribution and/or Service (12b-1) fees	None
Other expenses	0.00%
Total annual operating expenses	0.03%

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. 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:

1 year	$	3
3 years	$	10
5 years	$	17
10 years	$	39

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 25% of the average value of its portfolio.

Principal Investment Strategies

The Bloomberg U.S. Long Treasury Bond Index is a market value-weighted index of investment-grade fixed-rate public obligations of the U.S. Treasury with maturities of ten years or more.

Derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.

Principal Investment Risks

Interest rate increases can cause the price of a debt security to decrease.

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.

A decline in the credit quality of an issuer or a provider of credit support (such as guarantees) or a maturity-shortening structure (such as demand and put features) for a security can cause the price of a security to decrease.

U.S. Treasury obligations are high-quality securities issued or guaranteed by the U.S. Treasury providing minimal risk of loss of principal if held to maturity. Fluctuations in interest rates may cause the market value of such securities to vary.

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.

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.

Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will fluctuate.

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 and an additional index over various periods of time. The additional index has characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for more recent performance information.

Year-by-Year Returns*

	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025
	1.12%	8.59%	-1.63%	14.22%	17.81%	-4.86%	-29.42%	3.18%	-6.18%	5.29%

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	22.24%	March 31, 2020
Lowest Quarter Return	-13.40%	March 31, 2021
Year-to-Date Return	0.00%	March 31, 2026

* The initial offering of Fidelity® Long-Term Treasury Bond Index Fund (formerly named Institutional Premium Class) took place on October 4, 2017. Returns prior to October 4, 2017 are those of the former Premium Class and have not been restated to reflect current fees.

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.

For the periods ended December 31, 2025	Past 1 year	Past 5 years	Past 10 years
Fidelity® Long-Term Treasury Bond Index Fund
Return Before Taxes	5.29%	-7.30%	-0.05%
Return After Taxes on Distributions	3.65%	-8.49%	-1.29%
Return After Taxes on Distributions and Sale of Fund Shares	3.12%	-5.76%	-0.46%
Bloomberg U.S. Long Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)	5.59%	-7.23%	0.02%
Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)	7.30%	-0.36%	2.01%

* The initial offering of Fidelity® Long-Term Treasury Bond Index Fund (formerly named Institutional Premium Class) took place on October 4, 2017. Returns prior to October 4, 2017 are those of the former Premium Class and have not been restated to reflect current fees.

Investment Adviser

Fidelity Management & Research Company LLC (FMR) (the Adviser) is the fund's manager. Other investment advisers serve as sub-advisers for the fund.

Portfolio Manager(s)

Brandon Bettencourt (Co-Portfolio Manager) has managed the fund since 2014.

Mark Lande (Co-Portfolio Manager) has managed the fund since 2024.

Van Eswara (Co-Portfolio Manager) has managed the fund since 2025.

Purchase and Sale of Shares

You may buy or sell shares through a Fidelity® brokerage or mutual fund account, through a retirement account, or through an investment professional.

You may buy or sell shares in various ways:

Internet

www.fidelity.com

Phone

Fidelity Automated Service Telephone (FAST®) 1-800-544-5555

To reach a Fidelity representative 1-800-544-6666

Mail

Additional Purchases: Fidelity Investments P.O. Box 770001 Cincinnati, OH 45277-0003

Redemptions: Fidelity Investments P.O. Box 770001 Cincinnati, OH 45277-0035

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 fund, 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. Ask your investment professional or visit your intermediary's web site for more information.

"BLOOMBERG®" and the Bloomberg indices listed herein (the "Indices") are service marks of Bloomberg Finance L.P. and its affiliates, including Bloomberg Index Services Limited ("BISL"), the administrator of the Indices (collectively, "Bloomberg") and have been licensed for use for certain purposes by Fidelity. Bloomberg is not affiliated with Fidelity, and Bloomberg does not approve, endorse, review, or recommend the fund. Bloomberg does not guarantee the timeliness, accuracy, or completeness of any data or information relating to the fund.

Current regulations allow Fidelity to send a single copy of shareholder documents for Fidelity® funds, such as prospectuses, annual and semi-annual reports, and proxy materials, to certain mutual fund customers whom we believe are members of the same family who share the same address. For certain types of accounts, we will not send multiple copies of these documents to you and members of your family who share the same address. Instead, we will send only a single copy of these documents. This will continue for as long as you are a shareholder, unless you notify us otherwise. If at any time you choose to receive individual copies of any documents, please call 1-800-544-8544. We will begin sending individual copies to you within 30 days of receiving your call.

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. © 2026 FMR LLC. All rights reserved.

1.9885083.110

LBX-I-SUM-0426