Mark David McGwire, nicknamed "Big Mac", is an American former professional baseball first baseman who played 16 seasons in Major League Baseball (MLB) from 1986 to 2001 for the Oakland Athletics and the St. Louis Cardinals. He won two World Series championships, one with Oakland as a player in 1989 and one with St. Louis as a coach in 2011. One of the most prolific home run hitters in baseball history, McGwire hit 583 home runs during his career, which ranked 5th-most in MLB history at the time of his retirement and currently ranks 11th. He holds the major-league career record for at bats per home run ratio (10.6), and is the former record holder for both home runs in a single season and home runs hit by a rookie. McGwire was one of several central figures in baseball's steroids scandal.

The Oakland Athletics are an American professional baseball team based in Oakland, California. The Athletics compete in Major League Baseball (MLB) as a member club of the American League (AL) West Division. The team currently plays its home games at the Oakland Coliseum, with plans to temporarily move to Sutter Health Park in West Sacramento, California, for the 2025–2027 seasons, prior to their permanent move to Las Vegas. The nine World Series championships, fifteen pennants, and seventeen division titles that the A's have won throughout their history is the second-highest in the American League after the New York Yankees.