Mark Alan Williamson (born July 21, 1959) is a retired professional baseball player who played pitcher in the Major Leagues from 1987 to 1994. He played for the Baltimore Orioles. On April 29, 1988, Williamson pitched 6 shutout innings to help the Orioles defeat the White Sox 9-0. The victory snapped the Orioles 21 game losing streak that started the 1988 season. On July 13, 1991, he pitched a no hitter along with Bob Milacki, Mike Flanagan, and Gregg Olson against the Oakland Athletics. As of 2018, Mark is a real estate broker in the San Diego, CA suburbs.