Juan Martín del Potro defeated five-time defending champion Roger Federer in the final, 3–6, 7–6(7–5), 4–6, 7–6(7–4), 6–2 to win the men's singles tennis title at the 2009 US Open.

De Potro was the first Argentine to win the title since Guillermo Vilas in 1977.

He was also vying to become the first man to win the Surface Slam (winning majors on clay, grass and hard court in the same calendar year), having won the French Open and Wimbledon.

This was the first major since the 2006 Australian Open not to have Federer and Nadal as the top two seeds.

2 ranking after Murray lost to Marin Čilić in the fourth round.