Clijsters was born on June 8, 1983, in Bilzen, Limburg, in the Flemish Region of Belgium. She is the daughter of Lei Clijsters, a former footballer, and Els Vandecaetsbeek, a former national gymnastics champion. Lei Clijsters died of lung cancer on 4 January 2009. Clijsters says that she inherited footballer's legs from her father and a gymnast's flexibility and stamina from her mother and her tennis instructor. Kim's younger sister Elke finished 2002 as the ITF World Junior Doubles champion and retired in 2004 after back injuries.
In December 2003, Clijsters announced her engagement to Australian Lleyton Hewitt, but their relationship ended in October 2004. In October 2006, Clijsters announced her engagement to American basketball player Brian Lynch, who is based in Kim's hometown of Bree. Clijsters gave birth to a daughter Jada Ellie on 25 February 2008.
Clijsters has won 39 WTA singles titles and 11 WTA doubles titles. She has won three Grand Slam singles titles at the US Open in 2005, 2009 and 2010. She has also won the WTA Tour Championships singles title in 2002 and 2003. In doubles, she won the French Open and Wimbledon titles in 2003. Clijsters was twice a singles runner-up at the French Open and a one-time runner-up at the Australian Open, also reaching two Wimbledon singles semi-finals. She announced her retirement with immediate effect on 6 May 2007, but almost two years later, on 26 March 2009, she publicly declared her intent to return to the WTA tour for the 2009 summer hard court season. In only her third tournament back, she won her second US Open title, becoming the first unseeded player and wildcard to win the tournament, and the first mother to win a major since Evonne Goolagong in 1980. Clijsters is popularly known as one of the "comeback queens" of tennis.
In 2001 Clijsters became the first Belgian—man or woman—to reach a Grand Slam singles final in the Open Era. In 2003 Clijsters became not only the first Belgian—man or woman—to be ranked World No. 1, but also did so without winning a Grand Slam tournament. Clijsters is one of only five women to have been ranked World No. 1 in singles and doubles simultaneously (the others being Martina Navratilova, Martina Hingis, Serena Williams, Arantxa Sánchez Vicario and Lindsay Davenport). Clijsters compiled a 90–12 singles record. Her singles win total was the highest single-season total by any woman since Navratilova in 1982. Clijsters was the first woman to play more than 100 singles matches in a year since Chris Evert in 1974.
In returning to the World No. 1 ranking after the Australian Open in January 2006, Clijsters broke a rankings record. She was ranked as low as World No. 134 in March 2005, so her return to the top spot in a ten-month span was the fastest and biggest leap in women's tennis history.
In 2010 First woman to retain the US Open title since Venus Williams in 2001. Second woman in the Open Era to win three successive US Opens in which she played. 21 consecutive US Open match victories, second all-time to Chris Evert's 31 from 1975-1979. Third woman to win two Grand Slams as a mother, one shy of the record by Margaret Court. Repeated her own 2005 feat of winning a women's sport record paycheck of US$2.2 million Broke the US$20 million mark in career prize money at the US OpenFor her performance during the season, Clijsters received the WTA Player of the Year 2010 award for the second time (first one in 2005), the first player ever to win this award in the year following the win of the Come Back Player of the Year.
