Leon Day (October 30, 1916 - March 13, 1995) was an American right-handed pitcher in the Negro Leagues. He played for the Baltimore Black Sox, the Brooklyn & Newark Eagles, and the Baltimore Elite Giants.
He was born in Alexandria, Virginia. Day is noted for pitching a perfect season in 1937 (13-0) while playing for the Newark Eagles, and for his fastball. Day was also a good hitter and baserunner, batting .320 in 1937.
From 1935 through 1946 he appeared in a record seven East-West All-Star Games, and set an all-star record by striking out 14 batters. Also, in 1942 he set a Negro League record when he struck out 18 Baltimore batters in a single game - including Roy Campanella three times.