The 2003 Arizona Diamondbacks season was the franchise's 6th season in Major League Baseball and their 6th season at Bank One Ballpark in Phoenix, Arizona, as members of the National League West. They looked to improve on their 98–64 record from 2002. They looked to contend in what was once again a strong National League West. They finished the season with a record of 84–78, good enough for third place in the division.

Offseason

Regular season

Season standings

National League West

Record vs. opponents

Notable transactions

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

Farm system