Strategy. Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds), of U.S. and non-U.S. issuers, including emerging markets countries. Emerging markets include countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by the World Bank, and other countries or markets that the Adviser identifies as having similar emerging markets characteristics. Potentially investing in non-income producing securities, including defaulted securities and common stocks. Investing in companies in troubled or uncertain financial condition. Allocating investments across different countries and regions. Investing in securities … Show more… Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds), of U.S. and non-U.S. issuers, including emerging markets countries. Emerging markets include countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by the World Bank, and other countries or markets that the Adviser identifies as having similar emerging markets characteristics. Potentially investing in non-income producing securities, including defaulted securities and common stocks. Investing in companies in troubled or uncertain financial condition. Allocating investments across different countries and regions. Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers. Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield. Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%). Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments. Reorganization. The Board of Trustees of Fidelity Summer Street Trust has unanimously approved an Agreement and Plan of Reorganization ("Agreement") between Fidelity Global High Income Fund and Fidelity High Income Fund. Each fund seeks a high level of current income. Growth of capital may also be considered. As a result of the proposed Reorganization, shareholders of each class of Fidelity Global High Income Fund would receive shares of the corresponding class of Fidelity High Income Fund. The Agreement provides for the transfer of all of the assets of Fidelity Global High Income Fund in exchange for corresponding shares of Fidelity High Income Fund equal in value to the net assets of Fidelity Global High Income Fund and the assumption by Fidelity High Income Fund of all of the liabilities of Fidelity Global High Income Fund. After the exchange, Fidelity Global High Income Fund will distribute the Fidelity High Income Fund shares to its shareholders pro rata, in liquidation of Fidelity Global High Income Fund. As a result, shareholders of Fidelity Global High Income Fund will become shareholders of Fidelity High Income Fund (these transactions are collectively referred to as the "Reorganization"). Shareholders of Fidelity Global High Income Fund have received a combined information statement and prospectus containing more information with respect to the Reorganization, and a summary of the Board's considerations in approving the Agreement. The Reorganization, which does not require shareholder approval, is expected to take place on or about September 13, 2024. The Reorganization is expected to be a tax-free transaction. This means that neither Fidelity Global High Income Fund nor its shareholders will recognize any gain or loss as a direct result of the Reorganization. Effective the close of business on March 22, 2024, new positions in Fidelity Global High Income Fund (the fund) may no longer be opened. Shareholders of the fund on that date may continue to add to their fund positions existing on that date. Investors who did not own shares of the fund on March 22, 2024, generally were not allowed to buy shares of the fund except that new fund positions could be opened: 1) by participants in most group employer retirement plans (and their successor plans) if a qualifying fund is already established as an investment option under the plans (or under another plan sponsored by the same employer), 2) by participants in a 401(a) plan covered by a master record keeping services agreement between Fidelity and a national federation of employers that included a qualifying fund as a core investment option, 3) for accounts managed on a discretionary basis by certain registered investment advisers that have discretionary assets of at least $500 million invested in mutual funds and already included the fund in their discretionary account program, 4) by a mutual fund or a qualified tuition program for which Fidelity serves as investment manager, 5) by a portfolio manager of the fund, 6) by a fee deferral plan offered to trustees of certain Fidelity funds, if the fund is an investment option under the plan, and 7) by qualified intermediaries to facilitate in-kind redemption activity when deemed by the Adviser to be in the best interests of the fund, and 8) by certain asset pools associated with an organization that already offers a qualifying fund as an investment option in its retirement plan(s). These restrictions generally will apply to investments made directly with Fidelity and investments made through intermediaries. Investors may be required to demonstrate eligibility to buy shares of the fund before an investment is accepted. Effective after the close of business on May 20, 2024, new positions in the fund may no longer be opened. Existing shareholders may continue to hold their shares and purchase additional shares through the reinvestment of dividend and capital gain distributions until the fund's Reorganization takes place. In connection with the Reorganization, an information statement/prospectus that was included in a registration statement on Form N-14 was filed with the Securities and Exchange Commission. Shareholders should read the information statement/prospectus, which contains important information about the Reorganization. For a free copy of the information statement/prospectus, please contact Fidelity at 1-800-544-8544. The information statement/prospectus is also available on the Securities and Exchange Commission's website (www.sec.gov). For more detailed information, please contact Fidelity at 1-800-544-8544. Show less