The 2003 Boston Red Sox season was the 103rd season in the franchise's Major League Baseball history. The Red Sox finished second in the American League East with a record of 95 wins and 67 losses, six games behind the New York Yankees, who went on to win the AL championship. The Red Sox qualified for the postseason as the AL wild card, and defeated the American League West champion Oakland Athletics in the ALDS. The Red Sox then lost to the Yankees in the ALCS.
 The Red Sox led the major leagues in nearly all offensive categories, including runs scored (961), batting average (.289), on-base percentage (.360), and perhaps most impressively, a .491 team slugging percentage, which set a new record previously held by the 1927 Yankees. It would stand until the 2019 season when the Astros (.495) and Twins (.494) both surpassed them. They also had 649 extra-base hits, the most ever by one team in a single season.
 In May 2003, the Red Sox settled a lawsuit in federal court filed by seven men who claimed to have been sexually abused as boys by Red Sox clubhouse attendant Donald James Fitzpatrick at the team's spring training site in Winter Haven, Florida between 1971 and 1991. The lawsuit requested $3.15 million in damages but the terms of the settlement were not disclosed.
 This was the first season with designated hitter David Ortiz, as he signed a contract for the Red Sox during the offseason. He would stay with the Red Sox until his retirement in 2016.
 Lucchino initially attempted to hire J. P. Ricciardi, the general manager of the Blue Jays, but Ricciardi rejected the offer and instead signed a long-term contract with the Blue Jays.
 On November 10, 2002, Oakland Athletics General Manager, Billy Beane, accepted an offer to become the new general manager of the Red Sox. Beane had for several years publicly expressed his interest in joining the Red Sox, and his contract with Oakland included a stipulation that would allow Beane to consider an offer from the Red Sox. Beane had yet to sign the contract with the Red Sox, a contract in which he would be guaranteed $12.5 million over five years, the most anyone had been given to run a baseball team. The following day, however, Beane shocked the Red Sox when he declared that he would not accept their offer; the move to Boston would limit the amount of time that Beane would have to spend with his daughter. 
 On November 25, 2002, Theo Epstein, 28, was hired as general manager of the Boston Red Sox. Epstein's hiring made him the youngest general manager in major league history. 
 
 Infielders
 Designated hitters
 Coaches
 Note: Pos = Position; G = Games played; AB = At bats; H = Hits; Avg. = Batting average; HR = Home runs; RBI = Runs batted in
 Note: G = Games played; AB = At bats; H = Hits; Avg. = Batting average; HR = Home runs; RBI = Runs batted in
 Note: G = Games pitched; IP = Innings pitched; W = Wins; L = Losses; ERA = Earned run average; SO = Strikeouts
 Note: G = Games pitched; IP = Innings pitched; W = Wins; L = Losses; ERA = Earned run average; SO = Strikeouts
 Note: G = Games pitched; W = Wins; L = Losses; SV = Saves; ERA = Earned run average; SO = Strikeouts
 As the AL wild card, the Red Sox entered the first round of the playoffs against the Oakland Athletics.  Despite losing the first two games in Oakland, Boston rebounded with two dramatic wins in the late innings at Fenway Park to even the series.  When the series returned to Oakland, the Red Sox held off a late Oakland charge to win the series in five games.  In doing so, they joined the 1995 Mariners and 1999 Red Sox in coming back from a two-game deficit to win a best-of-five ALDS.
 Boston wins the series, 3–2
 The stage was set for a classic showdown with longtime division rival, the New York Yankees.  The teams split the first two games in the Bronx before the real drama unfolded in Game 3 at Fenway Park.  A highly anticipated matchup between Sox ace Pedro Martínez and former Sox' pitcher Roger Clemens turned ugly early on.  Karim García was hit in the back by a Martínez fastball.  Words were exchanged and Martínez threateningly gestured towards Yankee catcher Jorge Posada. When Garcia was forced out at second, he slid hard into Todd Walker.  The following inning, Manny Ramírez took exception to a high Clemens pitch and charged the mound. Both benches cleared, but the resulting brawl turned surreal when 72-year-old Yankee bench coach Don Zimmer charged Martínez. Martínez sidestepped and threw Zimmer to the ground.  After a thirteen-minute delay, Clemens struck out Ramírez and proceeded to pitch effectively as the Yankees took a 2–1 series lead.  The Red Sox won Game 4, but the Yankees won Game 5 to take the series' lead back to New York.  But Boston proved resilient, and their offense came alive for the first time in the series to the tune of nine runs on sixteen hits to force a seventh game.  With a 4–0 lead early on and Martínez pitching, Boston appeared to be on the brink of winning the pennant.  But when Martinez started to get tired in the end of the 6th inning, instead of taking him out as he always had in that situation, manager Grady Little not only left him in to finish the inning, but sent him out in the seventh and the eighth. despite allowing several baserunners. Predictably, the Yankees tied the game 5–5 with three eighth-inning runs off Martínez, sending the game on into the October night.  Yankee closer Mariano Rivera pitched three scoreless innings, and in the bottom of the eleventh, Aaron Boone turned on the first offering from Tim Wakefield and sent it into the frenzied bleachers of Yankee Stadium, sending the Yankees on to the World Series for the fifth time in six years.  This game further cemented the legend many believed was The Curse of the Bambino.
 New York wins the series, 4–3
 The Portland Sea Dogs replaced the Trenton Thunder as the Red Sox' Double-A affiliate. The Red Sox fielded two teams in the Dominican Summer League, while not participating in the Venezuelan Summer League, following the Venezuelan general strike of 2002–03.
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