2011 Major League Baseball wild card chase

The 2011 Major League Baseball wild card chase was a playoff chase involving the Boston Red Sox and Tampa Bay Rays in the American League and the Atlanta Braves and St. Louis Cardinals in the National League.

On September 2, the Red Sox and Braves led the American League and National League wild card races by 9 and 8+1⁄2 games, respectively. Over the next 24 games, the Red Sox went 7–17, while the Braves went 8–16; in the same timespan, the Rays and Cardinals each won 16 games to tie for the wild cards going into Game 162 on September 28, with the rallying teams both being set to host Game 163, if it was necessary. On September 28, the last day of the 2011 regular season, the postseason fate of these four teams fighting for two playoff spots across both leagues was decided.

In the American League, the Rays defeated their American League East division rivals, the New York Yankees, with dramatic home runs in the 9th inning by Dan Johnson and later in the 12th inning by Evan Longoria to win the American League wild card berth after the Baltimore Orioles defeated the Red Sox on a walk-off single. In the National League, the Cardinals defeated the Houston Astros to win the National League wild card berth after the Braves lost to the Philadelphia Phillies in 13 innings.

The Red Sox and Braves became the first teams in history to hold leads as large as eight games in September and miss the postseason. Sports Illustrated writer Tom Verducci called the events of September 28 "the most thrilling 129 minutes in baseball history." The Cardinals eventually rode the momentum of their win to win the NLDS and NLCS on their way to defeating the Texas Rangers for their 11th World Series title.

The 2011 season was the final season of the single wild card format, as MLB added second wild card teams to each league starting with the 2012 season.