William Hillyer Lyon was an American football coach. He served as the head football coach at the University of Mississippi (Ole Miss) in 1899. During his one-season tenure at Mississippi, Lyon compiled an overall record of three wins and four losses (3–4). Lyon was born in 1872 in Boonton, New Jersey. He was a member of the Phi Delta Theta fraternity. In 1906, Lyon was working for a lumber company in Bridgeport, Connecticut as a travelling salesman. By the time of World War I, Lyon living in Bridgeport working as an accountant for the United States Government. He died in Stamford in 1957.