John Joseph "Jack" O'Neill (10 January 1873 – 29 June 1935) was catcher in Major League Baseball who played for the St. Louis Cardinals (1902–03), Chicago Cubs (1904–05) and Boston Beaneaters (1906). He batted and threw right-handed. He was born in the townland of Tawnaleen, near Maum, in County Galway, Ireland, to Michael O'Neill, a small farmer in Maum, and Mary Joyce. O'Neill was one of four major league brothers. Steve was a catcher and manager, Jim a shortstop, and Mike, who also was born in Ireland, was a pitcher and formed a brother battery with Jack for the St. Louis Cardinals.