Rafael Nadal of Spain officially moved into the No. 1 position on Monday with the release of the latest rankings of the Association of Tennis Professionals.
Nadal has 6,700 points, ahead of Roger Federer at 5,930.
Federer had held the top spot since early in February 2004, a record 237 consecutive weeks.
Nadal has enjoyed a dream summer, winning the French Open and Wimbledon over Federer, and taking the Queen's championship in London, England, and the Rogers Cup in Toronto.
"The feeling for sure is very happy for being No. 1, but the feeling doesn't change too much because the last years I did very well too," Nadal said on Sunday from Beijing, where he captured the gold medal by defeating Fernando Gonzalez of Chile in straight sets.
Nadal has won major titles on clay, grass and hardcourts in the last three months, and has only lost to Novak Djokovic of Serbia, at the Cincinnati Masters. He avenged that defeat in the Olympic semis.
There were no major changes in the ATP top 10. U.S. player James Blake, who played well in the Olympics, dropped two spots from No. 7 due to some poor results on the pro tour.
Andy Roddick of the U.S. and David Nalbandian of Argentina each moved up a spot as a result.
Gonzalez moved up four spots to No. 11.
Frank Dancevic of Niagara Falls, Ont., is ranked No. 147.
The final Grand Slam event of the season, the U.S. Open, begins in earnest on Aug. 25.