Justine Henin
Another star who started and ended young, Belgian Justine Henin was a force to be reckoned with in women’s tennis in the 2000s, using her trademark backhand to win seven Grand Slam singles titles, two of them at the French Open without losing a single set, as well as an Olympic Gold Medal in 2004. At the time she retired in 2008, Henin was ranked the world No. 1 in women’s tennis, and though she returned briefly in 2010, an elbow injury forced a second retirement the following year.