William Thomas Clark (June 29, 1831 – October 12, 1905) was an American soldier and politician, serving as a general in the Union army during the American Civil War and as a reconstruction era U.S.

He became a school teacher and moved in 1854 to New York City, where he passed the bar exam.

At the beginning of the Civil War, he became a lieutenant and adjutant of the 13th Iowa Infantry Regiment.

He was made a brevet brigadier general for service in the Atlanta Campaign and was assigned to an infantry brigade in the XV Corps during the Carolinas Campaign, but was only lightly engaged in fighting.

As a representative from Texas in Congress in 1870–72, he obtained the first appropriation for the harbor of Galveston ($100,000), making possible the completion of the jetties there.