Nuveen Select Tax-Free Income Portfolio 3 is a diversified closed-end management investment company. The Fund's investment objective is that it 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's portfolio composition includes various sectors, such as tax obligation/limited, tax obligation/general, healthcare, transportation, consumer staples, the United States guaranteed and Other. The Fund's portfolio spans various states and territories, including California, Illinois, Texas, New Jersey, Colorado, Washington, Florida, Virginia, New York, Missouri, Iowa, Michigan, Minnesota, Nevada and Other. The Fund's investment advisor is Nuveen Fund Advisors, LLC, which is a subsidiary of Nuveen Investments, Inc. (Nuveen).