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.

Caroline Wozniacki (born 11 July 1990) is a Danish professional tennis player. She is a former world no. 1 on the WTA Tour. As of 23 January 2012, she held this position for 67 weeks. She is the first Scandinavian woman to hold the top ranking position and 20th overall.

Since her WTA debut in 2005, she has improved her year-end ranking each year until finishing on top in both 2010 and 2011. She has won 18 WTA singles titles as of August 2011, three in 2008, three in 2009, six in 2010 (the most since Justine Henin's ten in 2007), and six in 2011. She was runner-up at the 2009 US Open and the 2010 WTA Tour Championships in Doha to Kim Clijsters. She won the 2006 Wimbledon Girls' Singles title but has yet to win a women's Grand Slam title. She also holds two WTA titles in doubles.

Wozniacki is the daughter of Polish Roman Catholicimmigrants, Piotr and Anna Wozniacki. Anna played on the Polish women's national volleyball team, and Piotr played professional football. The couple moved to Denmark when Piotr signed for the Danish football club Boldklubben 1909. Wozniacki's older brother Patrik Wozniacki is a professional footballer for Hvidovre IF in Denmark.

Martina Hingis (born 30 September 1980) is a retired Swiss professional tennis player who spent a total of 209 weeks as World No. 1. She won five Grand Slam singles titles (three Australian Opens, one Wimbledon, and one US Open). She also won nine Grand Slam women's doubles titles, winning a calendar year doubles Grand Slam in 1998, and one Grand Slam mixed doubles title.

Hingis set a series of "youngest-ever" records before ligament injuries in both ankles forced her to withdraw temporarily from professional tennis in 2002 at the age of 22. After several surgeries and long recuperations, Hingis returned to the WTA tour in 2006. She then climbed to world number 6 and won three singles titles. On 1 November 2007, Hingis announced her retirement from tennis after testing positive for cocaine during Wimbledon in 2007. She denied using the drug, but decided not to appeal the imminent ban.

In June 2011, she was named one of the "30 Legends of Women's Tennis: Past, Present and Future" by Time.

Hingis was born in Košice, (then part of Czechoslovakia, now in modern Slovakia), to accomplished tennis players Melanie Molitorová and Karol Hingis. Molitorová was a professional tennis player, who was once ranked tenth among women in Czechoslovakia, and was determined to develop Hingis into a top player as early as pregnancy. Her father was ranked as high as nineteenth in the Czechoslovakian tennis rankings. Hingis's parents divorced when she was six, and she and her mother relocated around a year later to Trübbach in Switzerland. Her father, who continued to live in Košice as a tennis coach, said in 1997 that he had seen little of his daughter after the split.