Esther Mary Vergeer is a Dutch former professional wheelchair tennis player. Vergeer won 43 major titles, 23 year-end championships, and seven Paralympic gold medals. She was the world No. 1 in women's wheelchair singles from 1999 to her retirement in February 2013. Vergeer went undefeated in singles for ten straight years, ending her career on a winning streak of 470 matches. She has often been named the most dominant player in professional sports.

Wheelchair tennis is one of the forms of tennis adapted for wheelchair users. The size of the court, net height and rackets are the same, but there are two major differences from pedestrian tennis: athletes use specially designed wheelchairs, and the ball may bounce up to two times, where the second bounce may also occur outside the court.