Nuveen Select Tax-Free Income Portfolio 3 is a closed-ended investment company. The Fund seeks to provide current income and stable dividends, exempt from regular federal and designated state income taxes, where applicable, consistent with the preservation of capital by investing primarily in a portfolio of municipal obligations. The fund invests in municipal securities that are exempt from federal income taxes. The fund invests at least 80% of its managed assets in municipal securities rated investment grade (Baa/BBB or better by S&P, Moody's, or Fitch) at the time of investment. The fund may invest in inverse floating rate municipal securities, also known as tender option bonds. Nuveen Fund Advisors, LLC is the Fund's Adviser.