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.
When the Negro League was in the off-season, Day played winter ball in Puerto Rico. There he established a Puerto Rican record of 19 strikeouts.
During World War II Day served in the United States Army, and he was discharged in February 1946. That same month, he pitched an Opening Day no-hitter against the Philadelphia Stars.
In 1950 he left the United States to play in Canada for a year. The next two years he returned to play in the minor leagues, then returned to Canada to finish his career.
Day retired from baseball in 1955. He died of a heart attack in Baltimore, Maryland at age 78, just six days after learning he had been elected to the Baseball Hall of Fame.