Michael Joseph Sullivan (October 23, 1866 – June 14, 1906) was an American professional baseball player. He played in Major League Baseball as a right-handed pitcher from to for the Washington Nationals (1889), Chicago Colts (1890), Philadelphia Athletics (1891), New York Giants (1891 and 1896–97), Cincinnati Reds (1892–93), Washington Senators (1894), Cleveland Spiders (1894–95) and the Boston Beaneaters (1899).
He led the National League in win–loss percentage (.750) in 1892.
In 10 seasons he had a 54–65 win–loss record, 160 games (119 started), 99 complete games, 1 shutout, 40 games finished, 4 saves, innings pitched, 1,292 hits allowed, 892 runs allowed, 622 earned runs allowed, 45 home runs allowed, 568 walks allowed, 285 strikeouts, 18 hit batsmen, 76 wild pitches, a 5.04 ERA and a 1.674 WHIP.
Sullivan died in his hometown at the age of 39.