2009 US Open

The 2009 US Open was a tennis tournament played on outdoor hard courts, held from August 31 to September 14, 2009, in the USTA Billie Jean King National Tennis Center at Flushing Meadows, New York City, United States. Originally, it was scheduled to end with the men's singles final match on Sunday, September 13, but due to rain the tournament was extended by one day. Like the Australian Open, the tournament featured night matches.

Former World No. 1 and 2005 US Open women's singles champion, Kim Clijsters, competed in the 2009 US Open after being granted a wild card entry, returning to professional tennis after more than two years of retirement. She made it to the women's singles semi-finals, where she knocked out the defending champion Serena Williams in controversial circumstances. In the final, Clijsters defeated Caroline Wozniacki, the first Dane, man or woman, to reach a Grand Slam final in the Open Era, in straight sets: 7–5, 6–3. Clijsters thus became the first mother to win a Grand Slam since Evonne Goolagong Cawley in 1980. In the process, she also became the first unseeded player and wildcard to win the tournament.