William Windom (May 10, 1827 – January 29, 1891) was an American politician from Minnesota. He served as U.S. Representative from 1859 to 1869, and as U.S. Senator from 1870 to January 1871, from March 1871 to March 1881, and from November 1881 to 1883. He also served two non-consecutive times as Secretary of the Treasury from March to November 1881, and from 1889 to 1891, under three Presidents. He was a Republican. He was the great-grandfather of actor William Windom, who was named for him.