| Tournament details | |
|---|---|
| Dates | October 4–20, 1990[1] |
| Teams | 4 |
| Final positions | |
| Champions | Cincinnati Reds (5th title) |
| Runner-up | Oakland Athletics (13th World Series appearance) |
| Tournament statistics | |
| MVP | José Rijo (CIN) |
The 1990 Major League Baseball postseason was the playoff tournament of Major League Baseball for the 1990 season. The winners of each division advance to the postseason and face each other in a League Championship Series to determine the pennant winners that face each other in the World Series.
In the National League, the Cincinnati Reds and Pittsburgh Pirates both returned to the postseason for the first time since 1979. In the American League, the Boston Red Sox reached the postseason for the third time in five years, and the Oakland Athletics made their third consecutive appearance. The same four teams – the Reds, Pirates, Red Sox, and Athletics – had qualified for the postseason fifteen years before. They would all return again under an expanded format in the 2013 postseason.
This was the last edition of the postseason until 2006 to not feature the Atlanta Braves, who would make fourteen straight postseason appearances from 1991 to 2005, excluding 1994, when the season was cancelled due to a strike.
The playoffs began on October 4, 1990, and concluded on October 28, 1990, with the Reds shocking the defending World Series champion Athletics in a 4-game sweep to win their first title since 1976. It was the Reds’ fifth title in franchise history.