The 2009 Legg Mason Tennis Classic (also known as the 2009 Legg Mason Tennis Classic presented by GEICO for sponsorship reasons) was a men's tennis tournament played on outdoor hard courts. It was the 41st edition of the event known that year as Legg Mason Tennis Classic, and was part of the ATP World Tour 500 series of the 2009 ATP World Tour. It took place at the William H.G. FitzGerald Tennis Center in Washington, D.C., United States, from August 1 through August 9, 2009. The Legg Mason Tennis Classic was the third ATP stop of the 2009 US Open Series. Unlike previous years, the men's event was field 48 players instead of 32. Second-seeded Juan Martín del Potro won the singles title.

Finals

Singles

🇦🇷 Juan Martín del Potro defeated 🇺🇸 Andy Roddick, 3–6, 7–5, 7–6(8–6).

Doubles

🇨🇿 Martin Damm / 🇸🇪 Robert Lindstedt defeated 🇵🇱 Mariusz Fyrstenberg / 🇵🇱 Marcin Matkowski, 7–5, 7–6(7–3).

ATP entrants

List of Association of Tennis Professionals (ATP) singles entrants, as of July 27, 2009.

Seeds

Other entrants

The following players received wildcards into the singles main draw The following players received entry from the qualifying draw: The following player received the lucky loser spot: