William Halsey may refer to:

• William Halsey Jr. (1882–1959), U.S. Naval officer and the commander of the United States Third Fleet during part of the Pacific War against Japan.
• William F. Halsey Sr. (1853–1920), his father, U.S. naval officer
• William Darrach Halsey, American encyclopaedist and lexicographer
• William Melton Halsey (1915-1999), American abstract artist
• William Halsey (mayor) (1770–1843), mayor of Newark, New Jersey, 1836–1837
• William Halsey (judge), Irish politician, soldier and judge