Henin-Hardenne is a four-time Grand Slam tournament winner and in 2003 became the #1-ranked women's tennis player in the world. She won her first WTA Tour event as a pro, at Antwerp in 1999, becoming only the fifth person ever to win her WTA debut. Her breakout year was 2001, when she made the semifinals of the French Open (losing to fellow Belgian Kim Clijsters) and then the singles finals at Wimbledon (losing to Venus Williams). By the end of that year she was ranked #7 in the world and was a sports hero in her home country. In 2003 she began a stirring rivalry with Clijsters in Grand Slam tournaments: she defeated Clijsters in the finals of the 2003 French Open and the 2003 U.S. Open, and then again in the finals of the 2004 Australian Open. In 2005 she again won the French Open, defeating Mary Pierce.

She married Pierre-Yves Hardenne on 16 November 2002, and changed her name from Henin to