Mark David McGwire (born October 1, 1963) is a former Major League Baseball player who played his major league career with the Oakland Athletics and the St. Louis Cardinals. He is replacing Hal McRae as the hitting coach for the St. Louis Cardinals for 2010.

For his career, McGwire averaged a home run once every 10.61 at bats, the lowest at bats per home run ratio in baseball history (Ryan Howard is second at 11.32 and Babe Ruth is third at 11.80). In 1987, he broke the single-season home run record for rookies, with 49. In 1998, McGwire and Sammy Sosa achieved national fame for their home run-hitting prowess in pursuit of Roger Maris' single season home run record; McGwire would break the record and hit 70* home runs that year. Barry Bonds now holds the record.