The 1891 Boston Beaneaters season was the 21st season of the franchise. The team finished first in the National League with an 87–51 record. After trailing the Chicago Colts by seven games in early September, the Beaneaters won 25 of their last 29 games to finish first in the league.

Regular season

Season standings

Record vs. opponents

Roster

Player stats

Batting

Starters by position

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

Other batters

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

Pitching

Starting pitchers

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

Relief pitchers

Note: G = Games pitched; W = Wins; L = Losses; SV = Saves; ERA = Earned run average; SO = Strikeouts