John J. Clements was an American professional baseball player. He played as a catcher in Major League Baseball for 17 seasons. Despite being left-handed, Clements caught 1,076 games, almost four times as many as any other left-handed player in major league history and was the last left-hander to catch on a regular basis. He is credited with being the first catcher to wear a chest protector.

Catcher is a position in baseball and softball. When a batter takes their turn to hit, the catcher crouches behind home plate, in front of the (home) umpire, and receives the ball from the pitcher. In addition to this primary duty, the catcher is also called upon to master many other skills in order to field the position well. The role of the catcher is similar to that of the wicket-keeper in cricket.