The 2009–10 season was the 115th in the history of Arsenal Football Club. It began on 1 July 2009 and concluded on 30 June 2010, with competitive matches played between August and May. The club ended the Premier League campaign in third position, 11 points behind champions Chelsea. In the domestic cup competitions, Arsenal were knocked out in the fourth round of the FA Cup to Stoke City and the fifth round of the League Cup against Manchester City. They failed to progress past the quarter-finals of the UEFA Champions League, losing to reigning champions Barcelona in a two-legged tie.
Arsenal did little business in the transfer market; their only outfield signing of the summer was defender Thomas Vermaelen from Ajax. Several players however left the club before the campaign got under way, including Emmanuel Adebayor and Kolo Touré in separate deals to Manchester City. To reinvigorate the side and benefit from Cesc Fàbregas's creativity, manager Arsène Wenger instituted a fluid 4–3–3 formation. The team made an impressive start; by November they had scored 36 goals in 11 league games and qualified for the Champions League knockout stage with a game to spare. Arsenal's defensive fragility was a recurring theme throughout the season and meant the team struggled to sustain a title challenge; they suffered back-to-back Premier League losses on four occasions.
41 different players represented Arsenal in four competitions and there were 14 different goalscorers. Arsenal's top goalscorer was Fàbregas, who scored 19 goals in 36 appearances.