Spain's Rafael Nadal has replaced Roger Federer as the new world number one and Serbia's Ana Ivanovic toppled compatriot Jelena Jankovic at the top of the ATP rankings released on Monday.
Federer, 27, relinquishes his hold on the top spot after 237 weeks.
The Swiss player has struggled all season, while Nadal, 22, has played some of the best tennis of his career, winning eight titles including Roland Garros, Wimbledon and the Olympic gold.
Asked about his feelings on becoming number one, the Mallorcan left-hander, said: "I'm very happy to be number one. But the feeling doesn't change too much because the last years I did very well, too."
Ivanovic did not compete at the Beijing Olympics because of a thumb injury, while Jankovic reached the quarter-finals.
The French Open champion has a 97-point lead on Jankovic with Russia's Svetlana Kuznetsova, beaten in the first round in Beijing in third.
In men's ranking, Olympic finalist Fernando Gonzalez of Chile moves up four places to 11th, while Argentine Juan Martin Del Potro, winner of his fourth consecutive title in Washington yesterday after Kitzbuhel, Stuttgart and Los Angeles, moves to 17th.