William P. Mahoney (1882 – July 31, 1967) was an American lawyer and politician who served in the Arizona House of Representatives from 1915 to 1916 and in the Arizona Senate from 1917 to 1918, as a member of the Democratic Party. After his tenure in the state legislature he served as the sheriff of Mohave County, Arizona. Mahoney was appointed to the Department of Social Security and Public Welfare in 1937 and later served as its chair before resigning in 1952. He was appointed to the Arizona Employment Security Commission in 1955 and served until 1959.