American professional baseball (left-handed) pitcher who popularized the screwball pitch. In this pitch the ball, which is thrown with the same arm motion as a fastball, has reverse spin against the natural curve and, when thrown by a left-hander, breaks sharply down and away from right-handed batters.

Two of Hubbell's elder brothers were professional baseball pitchers, and they and his father trained him. From high school Hubbell went to the minor leagues (1923–25), and in 1925 he joined the Detroit Tigers of the American League, a team that did not allow screwball pitches and that sold his contract to the New York Giants of the National League in 1928.

With the Giants, Hubbell led the league in games won in 1933 (23 games), 1936 (26), and 1937 (22) in addition to winning 20 games or more in 1934 and 1935. In 1933 he pitched 46 consecutive scoreless innings, and in 1936–37 he won 24 consecutive games. In the 1934 All-Star game, Hubbell struck out in succession Babe Ruth (Ruth, Babe), Lou Gehrig (Gehrig, Lou), Jimmie Foxx (Foxx, Jimmie), Al Simmons, and Joe Cronin. In his 16-year career he had 253 wins and 154 losses, and he had an earned run average of 2.97; in World Series competition he won 4 games and lost 2. Following his retirement as a player in 1943, Hubbell first directed the Giants' farm system and then became a scout. He was elected to the Baseball Hall of Fame in 1947.