The 2009 Major League Baseball All-Star Game was the 80th midseason exhibition between the all-stars of the American League (AL) and the National League (NL), the two leagues comprising Major League Baseball. The game was held on July 14, 2009, at Busch Stadium in St. Louis, Missouri, the home of the National League St. Louis Cardinals. The game was the first All-Star Game held in St. Louis since 1966. This was the seventh year in which the All-Star Game determined home field advantage in the World Series, with the American League winning all seven games up to and including 2009 under this format. After the game, the National League led the series, 40–38–2, but had not won since 1996. Fox televised the contest, with Joe Buck and Tim McCarver in the booth for the game broadcast, joined at the bottom of the 2nd inning by President Barack Obama. Pre-game coverage began at 5 PM US EDT on MLB Network, with ESPN joining in at 7 PM US EDT. Outside the USA, Rogers Sportsnet (Canada) and ESPN America (Europe) carried MLB's international feed with their own video feed and announcers.

The Major League Baseball All-Star Game, also known as the "Midsummer Classic", is an annual professional baseball game sanctioned by Major League Baseball (MLB) and contested between the all-stars from the American League (AL) and National League (NL). Starting fielders are selected by fans, pitchers are selected by managers, and reserves are selected by players and managers.