The 1921 St. Louis Cardinals season was the team's 40th season in St. Louis, Missouri and the 30th season in the National League. The Cardinals went 87–66 during the season and finished third in the National League.

Regular season

Rogers Hornsby hit .397 in 1921, and his 21 home runs were second in the league. He also led the league in on-base percentage (.458), slugging percentage (.639), runs (131), RBI (126), doubles (44), and triples (18).

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

Other 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

Awards and honors

Farm system