John O'Neil

• John O'Neil (painter), American painter and writer
• John O'Neil (footballer), Scottish footballer
• John O'Neil (rugby union), American rugby union player
• John O'Neil (rugby league), English rugby league footballer who played in the 1950s and 1960s
• John O'Neil (baseball), American baseball player
• John G. A. O'Neil, American politician from New York
• John O'Neil (priest), Irish Anglican priest
• John E. O'Neil IV, U.S. Army officer
• John Jordan O'Neil, better known as Buck O'Neil, American baseball player

Fictional characters

• Mr. John O'Neil, a Teenage Mutant Ninja Turtles character