The most successful female tennis player of all time naturally comes with a price tag to match. In 2003 Nike reportedly spent $55 million on a sponsorship deal with Serena Williams, which, when adjusted for inflation, is an incredible $89.7 million (£74.2m).

The deal was set to last for five years, with the option to add a further three years at the end. It also included royalties and performance bonuses if Williams won any Grand Slam tournaments.

It’s safe to say that Nike got plenty of on-court endorsement for its money: Williams won a remarkable 23 Grand Slam titles throughout her career, with 19 of the victories happening after she partnered with the activewear brand.

Williams announced her retirement from tennis in August 2022. Nike aside, she's also endorsed the likes of dating app Bumble, Beats headphones by Dr. Dre, Berlei lingerie, Tempur-Pedic mattresses, and AccorHotels.

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