John J. O'Neill was a Major League player. He was born in New York City.
Little is known about this utility who played for the New York Giants in parts of two seasons. Used as a backup catcher for John Warner (1899) and Frank Bowerman (1902), O'Neill appeared in four games and went hitless in 15 at-bats (.000). As a catcher, he collected 19 outs with eight assists and committed four errors for a .931 fielding percentage.