William O'Neill
William, Billy or Bill O'Neill may refer to:
Politics
- Bill O'Neill (Ohio politician), former member of the Ohio House of Representatives
- Bill O'Neill (New Mexico politician), member of the New Mexico Senate
- C. William O'Neill, Governor of Ohio
- William O'Neill (Ohio judge), appellate judge and 2008 candidate for U.S. Representative from Ohio's 14th congressional district
- William A. O'Neill, Governor of Connecticut, 1980–1991
- William P. O'Neill, Lieutenant Governor of Indiana
Sports
- Bill O'Neill (American football), American football player
- Bill O'Neill (baseball), American baseball player
- Bill O'Neill (bowler), American professional ten-pin bowler
- Bill O'Neill (bowls), New Zealand lawn bowler
- Billy O'Neill (rugby), Welsh rugby player
- William O'Neill (rugby union), Irish rugby union player
- Billy O'Neill (dual player), Irish former Gaelic football and hurler
- Billy O'Neill (footballer), Irish footballer
- Willie O'Neill (footballer, born 1940), Scottish footballer
- Willie O'Neill (Wexford hurler), Irish hurler
- Willie O'Neill (Cork hurler), Irish hurler and Gaelic footballer
- Willie O'Neill (Irish footballer), Irish international footballer
Others
- Bill O'Neill (media), News Corporation executive
- Buckey O'Neill, Old West sheriff and U.S. Army officer killed at the Battle of San Juan Hill
- William F. O'Neil, founder of General Tire and Rubber Company
- William O'Neill, 1st Baron O'Neill, Anglo-Irish hereditary peer, clergyman and musical composer
- William O'Neill (Medal of Honor), American soldier in the Indian Wars