William Dunlap Simpson (October 27, 1823 – December 26, 1890) was the 78th governor of South Carolina from February 26, 1879, when the previous governor, Wade Hampton, resigned to take his seat in the U.S. Senate, until 1880. That year Simpson resigned to become Chief Justice of the South Carolina Supreme Court. In 1880 he resigned after being appointed Chief Justice of the state Supreme Court. He served for ten years from 1880 until his death in 1890. He is buried at the Laurens City Cemetery.