ESPN is marking the 40th anniversary of Title IX by unveiling the top 40 female athletes of the past 40 years.
Serena Williams won her first Grand Slam singles title when she was just 17, at the 1999 U.S. Open.
In 2002-03, Williams won four in a row -- the Serena Slam -- becoming just the fifth woman to hold all major titles at once.
And despite injuries, surgeries and setbacks, Williams, the No. 10 woman in ESPN's countdown, has won a total of 13 majors and has remained the most feared women's player on the planet for more than a decade.
"I think she'll be known for her intensity," says Pam Shriver, a former top-10 player and now an ESPN analyst. "When she is at her most dominant, she might be the most intimidating player ever."
Earlier in this series:
No. 40: Diver Fu Mingxia
No. 39: Jockey Julie Krone
No. 38: Gymnast Mary Lou Retton
No. 37: Hockey player Cammi Granato
No. 36: Soccer player Kristine Lilly
No. 35: Basketball player Diana Taurasi
No 34: Volleyball player Flo Hyman
No. 33: Soccer player Abby Wambach
No. 32: Swimmer Mary T. Meagher
No. 31: Marathoner Joan Benoit
No. 30: Sprinter Gail Devers
No. 29: Basketball player Nancy Lieberman
No. 28: Marathoner Grete Waitz
No. 27: Soccer player Michelle Akers
No. 26: Basketball player Chamique Holdsclaw
No. 25: Swimmer Dara Torres
No. 24: Golfer Nancy Lopez
No. 23: Swimmer Tracy Caulkins
No. 22: Soccer player Marta Vieira da Silva
No. 21: Tennis player Venus Williams
No. 20: Figure skater Michelle Kwan
No. 19: Skier Lindsey Vonn
No. 18: Softball player Lisa Fernandez
No. 17: Basketball player Ann Meyers Drysdale
No. 16: Basketball player Sheryl Swoopes
No. 15: Swimmer Janet Evans
No. 14: Figure skater Katarina Witt
No. 13: Basketball player Cheryl Miller
No. 12: Sprinter Florence Griffith-Joyner
No. 11: Tennis player Billie Jean King