John Joseph (Jack) McMahon (December 3, 1928 – June 11, 1989) was a professional basketball player and coach. A 6'1" guard from St. John's University, McMahon was selected by the Rochester Royals in the 1952 NBA Draft. He played eight seasons in the NBA, for Rochester and the St. Louis Hawks.
John Henry McMahon (1869–1894) was a Major League Baseball first baseman and catcher. He played in 51 games, with a .243 batting average, for the New York Giants of the National League in 1892 and 1893.