Nuveen Select Maturities Municipal Fund is a diversified closed-end management investment company. The Fund seeks to provide current income exempt from regular federal income tax, consistent with the preservation of capital by investing in an investment-grade quality portfolio of municipal obligations with intermediate characteristics. It invests in municipal securities that are exempt from federal income taxes and of varying maturities targeting an overall intermediate duration profile. It invests approximately 80% of its managed assets in municipal securities rated investment grade at the time of investment, or, if they are unrated, are judged by the manager to be of comparable quality. It invests over 20% of its managed assets in municipal securities rated below investment quality or judged by the manager to be of comparable quality, of which over 10% of its managed assets may be rated below B-/B3 or of comparable quality. Its investment advisor is Nuveen Fund Advisors, LLC.