John Gill Valentine (November 21, 1855 – October 10, 1903) was an American pitcher and umpire in Major League Baseball who played one season as a player for the 1883 Columbus Buckeyes of the American Association, and later umpired from 1884 to 1888.

Born in Brooklyn, New York, he made his major league debut for the Buckeyes in 1883, his only season as a player, and compiled 13 games pitched, starting 12 and completing 11 of them.

He had a win-loss record of 2–10, with an earned run average of 3.53 in 102 innings pitched.

[1] Valentine was involved in a couple of notable games, including being behind the plate for two no-hitters.

[2][3] Valentine died at the age of 47 in Central Islip, New York, and is interred at Green-Wood Cemetery in Brooklyn.