The 1971 National League Championship Series was a best-of-five series that pitted the East Division champion Pittsburgh Pirates against the West Division champion San Francisco Giants. The Pirates won the Series three games to one and won the 1971 World Series against the Baltimore Orioles. The Giants did not return to the postseason until 1987. This was the third National League Championship Series in all. It was the first League Championship Series in either league that was not a sweep for the winning team (Baltimore swept Oakland in the 1971 ALCS).