Shaun Michael Marcum (born December 14, 1981) is an American professional baseball starting pitcher for the Milwaukee Brewers of Major League Baseball.
Marcum was born in Kansas City, Missouri and raised in Excelsior Springs, Missouri, where he attended Excelsior Springs High School. Marcum initially attended the University of Missouri, but transferred to Missouri State University, playing on the 2003 College World Series team.
Marcum was drafted by the Blue Jays in the third round, 80th overall, of the 2003 Major League Baseball Draft. Marcum quickly rose through the minor leagues and made his major league debut on September 6, 2005 as a late season call-up from the minors in September when rosters expanded. He made his debut against the Baltimore Orioles pitching one scoreless inning, giving up a hit and one walk and one strikeout. Marcum pitched 8 innings, giving up six hits, without surrendering a run during the month of September.