Normally investing at least 80% of assets in U.S. dollar-denominated municipal money market securities and high quality investment-grade municipal debt securities (i) whose interest is exempt from federal income tax and (ii) that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have positive environmental, social and governance (ESG) characteristics. Evaluating each security in which the fund invests using both a traditional municipal bond credit, structure and relative value analysis and a consideration of the Adviser's judgment about the security's ESG characteristics. When assessing a security's ESG characteristics and its eligibility for purchase, the Adviser considers the following, where available: (i) the sustainability practices of the security's issuer or obligor, as applicable (each, an "issuer"), based on an evaluation of such issuer's individual ESG profile; (ii) information on a security's use of proceeds; and (iii) any third-party designation as a green, sustainable or sustainability-linked bond. A security's positive ESG characteristics can be determined under any of those three factors. Using the Adviser's proprietary ESG ratings process to evaluate the current state of an issuer's sustainability practices using a data-driven framework that includes both proprietary and third-party data, and also provide a qualitative forward-looking assessment of an issuer's sustainability outlook provided by the Adviser's fundamental research analysts and ESG team. The Adviser's ESG ratings of issuers are derived from multiple factors, including an issuer's environmental profile, which may include, but is not limited to, carbon and toxic emissions, water management, waste management, and vulnerability to the physical impacts of climate change. An assessment of an issuer's social profile includes, but is not limited to, its approach to quality health care access, housing affordability, human capital management, community reinvestment, and safety. An assessment of an issuer's governance profile includes, but is not limited to, its principles of management, oversight and transparency, governance efficiency and structure, and consideration of anticompetitive practices. These factors are weighted based on how material the Adviser believes each factor is to an issuer's financial outlook, effectiveness at service delivery, and long-term sustainability, and not all factors may be applicable to all issuers. Issuers with an above average ESG rating as determined by the Adviser are considered to have positive ESG characteristics and well-managed ESG risks. Assessing a security's use of proceeds by considering factors that provide ESG characteristics, such as energy efficiency, environmentally sustainable management, and providing access to quality health care, essential services and affordable housing. The Adviser will generally consider bonds that finance education, health care, affordable housing, clean energy, municipal water and sewer, public transportation, and designated green bonds, among others, as having positive ESG characteristics. Managing the fund to have similar overall interest rate risk to the supplemental index. In addition to focusing on municipal securities with positive ESG characteristics, the Adviser analyzes the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Normally maintaining a dollar-weighted average maturity of one year or less. Normally investing in securities with a maximum maturity of four years. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.