| Date: | July 30 – August 7 |
| Edition: | 43rd |
| Category: | ATP World Tour 500 |
| Draw: | 48S / 16D |
| Prize Money: | $1,166,400 |
| Surface: | Hard / outdoor |
| Venue: | William H.G. FitzGerald Tennis Center |
| Location: | Washington, D.C., US |
| Champs: |  Radek Štěpánek[1] |
| Champd: |  Michaël Llodra /  Nenad Zimonjić |
| Main Name: | Washington Open (tennis) Washington Open |
The 2011 Legg Mason Tennis Classic was a men's tennis tournament played on outdoor hard courts. It was the 43rd edition of this event and was part of the ATP World Tour 500 series of the 2011 ATP World Tour. It took place at the William H.G. FitzGerald Tennis Center in Washington, D.C. in the United States from July 30 through August 7, 2011. Unseeded Radek Štěpánek won the singles title.
See main article: article and 2011 Legg Mason Tennis Classic – Singles. Radek Štěpánek defeated Gaël Monfils, 6–4, 6–4
See main article: article and 2011 Legg Mason Tennis Classic – Doubles. Michaël Llodra / Nenad Zimonjić defeated 
Robert Lindstedt / 
Horia Tecău, 6–7(3–7), 7–6(8–6), [10–7]
| Country | Player | Rank | Seed | |
|---|---|---|---|---|
| France | Gaël Monfils | 7 | 1 | |
| Mardy Fish | 9 | 2 | ||
| Serbia | Viktor Troicki | 15 | 3 | |
 Austria | Jürgen Melzer | 18 | 4 | |
 Spain | Fernando Verdasco | 20 | 5 | |
| Serbia | Janko Tipsarević | 23 | 6 | |
 Cyprus | Marcos Baghdatis | 25 | 7 | |
 Argentina | David Nalbandian | 28 | 8 | |
 Russian Federation | Nikolay Davydenko | 29 | 9 | |
| France | Michaël Llodra | 30 | 10 | |
| John Isner | 33 | 11 | ||
 Brazil | Thomaz Bellucci | 34 | 12 | |
| Kevin Anderson | 35 | 13 | ||
 Belgium | Xavier Malisse | 41 | 14 | |
| Russian Federation | Dmitry Tursunov | 46 | 15 | |
 Finland | Jarkko Nieminen | 53 | 16 |
The following players received wildcards into the singles main draw
The following players received entry from the qualifying draw:
See main article: 2011 Legg Mason Tennis Classic – Singles qualifying.
The following players received entry as lucky losers into the singles main draw:
