2001 Major League Baseball postseason

The 2001 Major League Baseball postseason was the playoff tournament of Major League Baseball for the 2001 season. The winners of the League Division Series would move on to the League Championship Series to determine the pennant winners that face each other in the World Series.

In the American League, the New York Yankees made their seventh straight postseason appearance, the Seattle Mariners and Oakland Athletics returned for the second straight year, and the Cleveland Indians returned for the sixth time in eight years. The 2001 Mariners set an MLB record by winning 116 games during the regular season. This postseason was also the most recent to feature the Mariners until 2022.

In the National League, the Atlanta Braves made their tenth consecutive postseason appearance, the St. Louis Cardinals returned for the second year in a row, the Houston Astros made their third appearance in the past four years, and the Arizona Diamondbacks made their second appearance in the past three years.

The September 11 terrorist attacks on New York and Washington, D.C. pushed the end of the regular season from September 30 to October 7. Because of the attack, the World Series was not completed until November 4. The 2001 World Series was the first World Series to end in November.

The postseason began on October 9, 2001, and ended on November 4, 2001, with the Diamondbacks shocking the three-time defending World Series champion Yankees in seven games in the 2001 World Series. It was the first major league championship won by a team from Arizona.