2011 Western & Southern Open – Men's singles

Andy Murray won the men's singles title at the 2011 Cincinnati Masters after Novak Djokovic retired from the final, with the scoreline at 6–4, 3–0. It was Murray's seventh Masters title. Djokovic's retirement in the final marked only his second defeat of the season.

Roger Federer was the two-time defending champion, but lost to Tomáš Berdych in the quarterfinals.

Seeds
The top eight seeds receive a bye into the second round. • # 🇷🇸 Novak Djokovic (final, retired due to sore shoulder)

• # 🇪🇸 Rafael Nadal (quarterfinals)

• # Roger Federer (quarterfinals)

• # 🇬🇧 Andy Murray (champion)

• # 🇪🇸 David Ferrer (third round)

• # 🇫🇷 Gaël Monfils (quarterfinals)

• # 🇺🇸 Mardy Fish (semifinals)

• # 🇨🇿 Tomáš Berdych (semifinals, retired due to shoulder injury)

• # 🇪🇸 Nicolás Almagro (third round)

• # 🇫🇷 Gilles Simon (quarterfinals)

• # 🇺🇸 Andy Roddick (first round)

• # 🇫🇷 Richard Gasquet (third round)

• # 🇷🇺 Mikhail Youzhny (first round)

• # 🇷🇸 Viktor Troicki (first round)

• # 🇫🇷 Jo-Wilfried Tsonga (second round)

• # Stanislas Wawrinka (first round)