Samantha Jane "Sam" Stosur (/ˈstoʊzə/ STOE-zer; born 30 March 1984) is an Australian professional tennis player. She is a former World No. 1 in doubles, a ranking which she held for 61 weeks, and a former World No. 4 in singles. Stosur won the 2011 US Open, defeating Serena Williams in the final and becoming the first Australian woman since Evonne Goolagong Cawley in 1980 to win a Grand Slam singles tournament. Stosur has won five other Grand Slam titles to date: the 2005 US Open and 2006 French Open in women's doubles; and the 2005 Australian Open, 2008 and 2014 Wimbledon Championships in mixed doubles. In addition, she was the runner-up of the singles event at the 2010 French Open, defeating four-time champion Justine Henin, World No. 1 Serena Williams, and World No. 4 Jelena Janković en route to the final. She also reached three additional semi-finals at the French Open in 2009, 2012, and 2016.