High Quality Content by WIKIPEDIA articles! Samantha Stosur was the defending champion, but she lost to Victoria Azarenka in the quarterfinals. Kim Clijsters, a three-time champion who was on a 22-match winning streak at Flushing Meadows, lost to Laura Robson for the first time in her career at the second round stage, bringing to a close her last professional singles tournament before retirement. Serena Williams won the her fourth US Open singles title after defeating Azarenka 6–2, 2–6, 7–5 in the final. With the victory, Williams became only the third woman in history to win Wimbledon, Olympics, and the US Open in the same season after Steffi Graf and her sister, Venus Williams.