1991 Pittsburgh Pirates season

The 1991 Pittsburgh Pirates season was the 110th in franchise history; the 105th in the National League. This was their 22nd season at Three Rivers Stadium. For the second consecutive season, the Pirates won the National League East title with a record of 98–64. The Pirates finished the season with the best record in Major League Baseball. They were defeated four games to three by the Atlanta Braves in the NLCS. During the season, John Smiley won 20 games – the last to do so for the Pirates in the 20th century.

Offseason

 * December 6, 1990: Zane Smith was signed as a free agent by the Pirates.
 * February 4, 1991: Mark Huismann was signed as a free agent by the Pirates.
 * March 21, 1991: Esteban Loaiza was signed as an amateur free agent by the Pirates.
 * March 29, 1991: Steve Carter was traded by the Pirates to the Chicago Cubs for Gary Varsho.

Game log

 * Legend:      = Win       = Loss Bold = Pirates team member
 * Legend:      = Win       = Loss Bold = Pirates team member

Awards and honors
1991 Major League Baseball All-Star Game
 * Bobby Bonilla, DH, starter
 * John Smiley, P, reserve

Player stats
''Note: G = Games played; AB = At bats; H = Hits; Avg. = Batting average; HR = Home runs; RBI = Runs batted in''
 * Batting

Note: G = Games pitched; IP = Innings pitched; W = Wins; L = Losses; ERA = Earned run average; SO = Strikeouts
 * Pitching

National League Championship Series
October 9: Three Rivers Stadium in Pittsburgh, Pennsylvania
 * Game 1

October 10: Three Rivers Stadium in Pittsburgh, Pennsylvania
 * Game 2

October 12: Atlanta–Fulton County Stadium in Atlanta
 * Game 3

October 13: Atlanta–Fulton County Stadium in Atlanta
 * Game 4

October 14: Atlanta–Fulton County Stadium in Atlanta
 * Game 5

October 16: Three Rivers Stadium in Pittsburgh, Pennsylvania
 * Game 6

October 17: Three Rivers Stadium in Pittsburgh, Pennsylvania
 * Game 7

Transactions

 * May 16, 1991: Mike York was traded by the Pirates to the Cleveland Indians for Mitch Webster.
 * June 11, 1991: Mark Huismann was released by the Pirates.