The 1991 Seattle Mariners season was the 15th since the franchise's creation. It was the first winning season in franchise history, as the Mariners finished fifth in the American League West with a record of .510. Home attendance at the Kingdome was the highest to date, exceeding 2.1 million. After the season, the contract of third-year manager Jim Lefebvre was not renewed despite his performance, and he was succeeded by third-base coach Bill Plummer in 1992. This was the last full season under the ownership of Jeff Smulyan; the club was sold the following July.

Offseason

Regular season

Season standings

Record vs. opponents

Notable transactions

Roster

Game log

Regular season

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