The 1990 National League Championship Series was played between the Cincinnati Reds (91–71) and the Pittsburgh Pirates (95–67). It was the first playoff appearance for both teams since 1979 and the fifth NLCS meeting overall with Cincinnati winning the Pennant in 1970, 1972, and 1975 while Pittsburgh won in 1979.

The Reds won the series 4–2 and eventually went on to sweep the defending World Champion Oakland Athletics in the World Series. This was the only NLCS during the 1990s that did not feature the Atlanta Braves and was the first of four straight to feature either the Philadelphia Phillies or the Pittsburgh Pirates.

Between Game 2 (in Cincinnati) and Game 3 (in Pittsburgh), the teams took two days off instead of the usual one. That Sunday, October 7, the Pittsburgh Steelers needed to use Three Rivers Stadium for their scheduled game against the San Diego Chargers, so Game 3 (and by extension, the rest of the series) was pushed back a day.

Cincinnati won the series, 4–2.

Thursday, October 4, 1990 (8:30PM EDT) at Riverfront Stadium in Cincinnati, Ohio

The Pirates took the first game of the LCS with a 4-3 victory. The game-winning run scored in the 7th when Andy Van Slyke hit a routine inning-ending flyout that was misjudged by Eric Davis in left-field, scoring Gary Redus.

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