0000225322 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:StockMarketVolatilityMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:ForeignExposureMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:RealEstateIndustryConcentrationMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:IssuerSpecificChangesMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:MidCapInvestingMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member oef:RiskNondiversifiedStatusMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member oef:RiskNotInsuredDepositoryInstitutionMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member oef:RiskLoseMoneyMember 2026-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member 2025-01-01 2025-12-31 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member 2025-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member 2024-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member oef:AfterTaxesOnDistributionsMember 2025-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member oef:AfterTaxesOnDistributionsMember 2024-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member oef:AfterTaxesOnDistributionsAndSalesMember 2025-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:C000251103Member oef:AfterTaxesOnDistributionsAndSalesMember 2024-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:IndexIXWEJMember 2025-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:IndexIXWEJMember 2024-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:IndexSP001Member 2025-09-29 2026-09-29 0000225322 fmr:FidelitySAIRealEstateFundProMember fmr:S000085735Member fmr:IndexSP001Member 2024-09-29 2026-09-29 iso4217:USD pure 485BPOS 2026-09-29 false 0000225322 N-1A Fidelity Summer Street Trust Fund Summary Fund: Fidelity® SAI Real Estate Fund Investment Objective Fidelity® SAI Real Estate Fund seeks above-average income and long-term capital growth, consistent with reasonable investment risk. The fund seeks to provide a yield that exceeds the composite yield of the S&P 500 ® Index. Fee Table The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. Shareholder fees 0 Annual Operating Expenses 0.0050 0 0.0001 0.0051 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: 52 164 285 640 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 31 % of the average value of its portfolio. 0.31 Principal Investment Strategies Normally investing at least 80% of assets in securities of companies principally engaged in the real estate industry and other real estate related investments. A real estate entity or real estate related investment is any company that is principally engaged in the real estate industry and includes commercial and residential mortgage-backed securities; debt securities of real estate entities; equity securities of entities whose primary assets are mortgage loans or commercial or residential mortgage-backed securities; REITs that either own properties or make construction loans and preferred stocks of REITs; real estate developers; companies with substantial real estate holdings; and other companies whose products and services are related to the real estate industry, such as building supply manufacturers, mortgage lenders, or mortgage servicing companies. The Adviser considers a company to be principally engaged in the real estate industry if (i) at least 50% of its assets, income, sales or profits are committed to, or derived from, the real estate industry, or (ii) a third party has given the company an industry or sector classification consistent with the real estate industry. 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. Normally investing primarily in common stocks. Investing in domestic and foreign issuers. Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments. Normally investing at least 80% of assets in securities of companies principally engaged in the real estate industry and other real estate related investments. Stock Market Volatility. 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. Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry. The value of securities of issuers in the real estate industry can be affected by changes in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, and the management skill and creditworthiness of the issuer. Issuer-Specific Changes. 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. Mid Cap Investing. 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. In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund. 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 performance of the fund's shares over the past 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. The information illustrates the performance of the fund's shares over the past 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. Past performance (before and after taxes) is not an indication of future performance. www.fidelity.com Year-by-Year Returns 0.0251    Highest Quarter Return 0.0342 2025-03-31    Lowest Quarter Return -0.0089 2025-06-30    Year-to-Date Return 0.1294 2026-06-30 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. 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. 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. Return Before Taxes 0.0251 -0.0209 Return After Taxes on Distributions 0.0168 -0.0292 Return After Taxes on Distributions and Sale of Fund Shares 0.0169 -0.0180 MSCI US IMI Real Estate 25/50 Linked Index 0.0331 -0.0123 S&P 500® Index 0.1788 0.1919 2024-09-04 A From September 4, 2024 .