Kim Clijsters was born on June 8, 1983 in Bilzen, Belgium. She was born to Lei a professional soccer player and Els. She first picked up a racket at an age of five. She wanted to pursue tennis as her passtime hobby but it was not too late when she realized that this could be her career path too.

She easily entered the juniors and won a number of trophies. Along with this she also won 1998 French Open Juniors doubles title, and a runner-up title at the 1998 Juniors Wimbledon. She was now preparing for the WTA tour. Kim came to public notice in 1999 at Antwerp. Although she could not win yet she reached the quarter finals. At Wimbledon she definitely made her presence felt everywhere. She defeated Amanda Coetzer but lost in the 4th round. Her next show of talent came at the U.S. Open. She reached the 3rd round and faced the eventual champion Serena Williams.

In 1998, she was the runner-up in the Wimbledon (A suburb of London and the headquarters of the club where annual international tennis championships are played on grass courts) junior singles event.

Kim Clijters has won 21 singles titles in her career so far. Two of those 21 titles, she won at the WTA Tour Championships in Los Angeles, California in 2002 and 2003, when she defeated Frenchwoman Amelie Mauresmo.

Kim Clijsters is often written off by critics as "too nice", although she smacks her groundstrokes with authority and defends as if her life depended on it.

She announced her engagement to long-time partner, Australian player Lleyton Hewitt in November 2003, but they split up in October 2004.