Seven of the 10 richest sportswomen in the world during the past year, according to Forbes, were tennis players, with Maria Sharapova top of the list with earnings of $29m (£18.9m).
The Russian's endorsements of $23m dwarfed the $6m she collected in prize-money for a 12-month period ending in June of this year.
Much of her income came from sportswear manufacturers Head and Nike, while the 26-year-old has also launched her own brand of sweets called Sugarpova.
Second in the list of leading female earners was Serena Williams of the United States ($20.5m), followed by China's Li Na ($18.2m) and Victoria Azarenka of Belarus ($15.7m).
Other tennis players in the top 10 are Caroline Wozniacki ($13.6m), Agnieszka Radwanska ($7.4m) and Ana Ivanovic ($7m).
The only three non-tennis players in the women's top-10 are American Nascar driver Danica Patrick ($15m), South Korean figure skater Kim Yuna ($14m) and US golfer Paula Creamer ($5.5m).