The 2006 American League Championship Series (ALCS), the second round of the 2006 American League playoffs, began on October 10 and ended on October 14. The Detroit Tigers defeated the Oakland Athletics 4 games to none to advance to the 2006 World Series, and became the fourth AL team to win 10 pennants, joining the New York Yankees (39), the Athletics (15), and the Boston Red Sox (11). Magglio Ordóñez's game-winning walk-off home run in the bottom of the 9th inning of Game 4 sealed the pennant for the Tigers. This ALCS marked the 5th different AL pennant winner in as many years (following 2005 with the White Sox, 2004 with the Red Sox, 2003 with the Yankees, and 2002 with the Angels).

The Athletics had defeated the Minnesota Twins 3 games to none in the AL Division Series, and the Tigers had defeated the Yankees 3 games to 1. The Tigers faced the National League champions St. Louis Cardinals in the World Series but fell to them by 4 games to 1. The Athletics had home-field advantage (despite the Tigers having a better record) because the Athletics were a division champion, but they effectively lost the advantage by losing Games 1 and 2 at home. The Tigers hosted Games 3 and 4.

The Athletics were seeking their first AL pennant since 1990, while the Tigers captured the league title for the first time since their win in the 1984 World Series. The series was a rematch of the 1972 American League Championship Series (then a best-of-five series), in which Oakland defeated Detroit in 5 games. Detroit manager Jim Leyland, who led the Florida Marlins to the 1997 World Series title, became the seventh manager in history to win pennants in both leagues.

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