
Serena.

Prize money: $7 million
Endorsements: $6 million
Caroline Wozniacki's endorsement partners include Adidas, Rolex, Usana, Babolat and more.
She also partnered with Ovvo Optics this year for her own sunglasses line.

Prize money: $5.7 million
Endorsements: $5.5 million
Sloane Stephens won her first Grand Slam title in 2017, the US Open.
As a result, there was a huge bump in her off-court income because of the new deals with Nike, Mercedes-Benz, Rolex, Colgate, Chocolate Milk and Biofreeze.

Prize money: $5.5 million
Endorsements: $5.5 million
Muguruza won her second Slam at Wimbledon last year and the title meant a big bonus from sponsor Adidas. It also helped her land a deal with Rolex.
She signed a deal with Evian for a multiyear, global marketing campaign.
She bagged other sponsors like Babolat, Beats by Dre, Rolex, Maui Jim sunglasses and Caser Seguros insurance.

Prize money: $1 million
Endorsements: $9.5 million
Sharapova was only 25 when she invested $500,000 to found candy company Sugarpova. Recently, expanded her brand via agreements with the Hudson Group and SBE Hotel Group. The brand is available in 22 countries, and sales should hit $20 million next year.

Prize money: $4.2 million
Endorsements: $6 million
Venus Williams, who is planning to play in the 2020 Olympics is at number six when it comes to the highest paid athletes.
Alcon tapped Williams this year to help launch a new lubricant to combat dry eye.

Endorsements: $8 million
PV Sindhu earned glory after winning the silver medal in the Olympics 2016.
The 23-year-old has a robust sponsor roster with Bridgestone, Gatorade, Nokia, Panasonic, Reckitt Benckiser, and several others.

Prize money: $6.2 million
Endorsements: $1.5 million
Tennis world number one Simona Halep is at number eight when it comes to the list of highest earners. She reached the Australian Open final in January. Nike inked the Romanian to a multiyear pact the following month.

Salary/prize money: $3 million
Endorsements: $4.5 million
The most successful female race car driver, who retired from full-time racing after the 2017 Nascar season.
She hung up her fire suit for good after the Indy 500 in May.
She launched a clothing line, Warrior by Danica Patrick, last year and authored the fitness book Pretty Intense.

Prize money: $3 million
Endorsements: $4 million
Adidas is the biggest endorsement deal for the German tennis ace, and she also counts Generali, Porsche, Rolex, SAP and Yonex among her sponsors.