Samantha "Sam" Jane Stosur (English pronunciation: /ˈstoʊzər/ STOH-zər, born 30 March 1984) is an Australian professional tennis player. She won the 2011 US Open singles title and was a finalist at the 2010 French Open. Stosur is ranked World No. 6 and her career high in singles is World No. 4, achieved on 21 February 2011. She is a former world No. 1 on the WTA Tour in doubles with Lisa Raymond from the United States.

Stosur was born in Brisbane, Queensland, the daughter of Tony and Diane, and has two brothers, Dominic and Daniel. She is of Polish descent through her grandfather. When she was six, the family house and business on the Gold Coast was destroyed by a flood, and the family moved to Adelaide. There she started playing tennis, when she was given a racquet for Christmas at the age of eight. While her parents worked long hours at the cafe they had started, Stosur played at local courts with older brother Daniel, who later encouraged their parents to take her to tennis lessons. Stosur attended Helensvale State High School on the Northern Gold Coast. She went away on her first overseas trip at the age of 13, competing in the World Youth Cup in Jakarta, Indonesia.

Serena Jameka Williams (born September 26, 1981) is an American professional tennis player and a former world no. 1. The Women's Tennis Association has ranked her world no. 1 in singles on five separate occasions. She became the world no. 1 for the first time on July 8, 2002 and regained this ranking for the fifth time on November 2, 2009. She is the only female player to have won over $35 million in prize money.

Her 27 Grand Slam titles places her ninth on the all-time list: 13 in singles, 12 in women's doubles, and 2 in mixed doubles. She is the most recent player, male or female, to have held all four Grand Slam singles titles simultaneously and only the fifth woman in history to do so. She was also the first woman, along with sister Venus Williams, to hold all four Grand Slam doubles titles simultaneously since Martina Hingis did so in 1998. Her 13 Grand Slam singles titles is sixth on the all-time list. Williams ranks fourth in Grand Slam women's singles titles won during the open era, behind Steffi Graf (22 titles) and Chris Evert and Martina Navratilova (18 titles each). She has won more Major titles in singles, doubles, and mixed doubles than any other active player, male or female.