Mark Edward Leiter (born April 13, 1963) is an American retired professional baseball pitcher.

He played in Major League Baseball (MLB) for the New York Yankees, Detroit Tigers, California Angels, San Francisco Giants, Montreal Expos, Philadelphia Phillies, Seattle Mariners, and Milwaukee Brewers from 1990 to 1999 and in 2001.

Drafted by the Baltimore Orioles in 1983, Leiter missed the 1986, 1987, and 1988 seasons due to a rotator cuff injury that required three surgeries.

Leiter's younger brother Al, son Mark Jr., and nephew Jack have pitched in the major leagues.

[4] Leiter attended Central Regional High School in Bayville, New Jersey, where he played baseball as a pitcher together with his brother Al and Jeff Musselman.

[8] He had two operations performed by Orioles doctors[7] and worked as a corrections officer at the Ocean County Jail for four months in 1987.

[7][9] Not wanting to end his baseball career, Leiter decided to have a third surgery,[10] which was performed by James Andrews in November 1987.

He pitched in baseball camps and as a semi-professional before his brother Al, now with the New York Yankees, secured a tryout for Mark.

[7] They promoted him back to the major leagues on September 10[14] and he finished the 1990 season with a 6.84 earned run average (ERA) in 26+1⁄3 innings pitched in eight games for the Yankees.

[19] On March 15, 1994, the Tigers released Leiter during spring training as they wanted to prioritize their younger pitchers.

[26] On July 30, 1996, the Giants traded Leiter to the Montreal Expos for Kirk Rueter and Tim Scott.

Al, now pitching for the New York Mets, encouraged the team to sign Mark and they offered him a non-roster invitation to spring training, which he accepted.

[32] Then on April 4, the Rockies traded Leiter, Mike DeJean, and Elvis Peña to the Milwaukee Brewers for Juan Acevedo, Kane Davis, and Jose Flores.