From tournament winnings to lucrative endorsement deals, it's no secret that professional athletes rake in substantial paychecks each year. And for the first time in 11 years, tennis player Serena Williams has surpassed rival tennis star Maria Sharapova to become the top-paid female athlete in the world, Forbes reported Monday.

Williams, 34, earned $28.9 million in the past 12 months alone, pushing her ahead of Sharapova, who earned $20 million in the same period. Williams, who has earned $77.6 million in prize money over her 15-year career, was ranked as the 47th-highest-paid athlete in 2015, according to a Forbes list that included both men and women. The top-earner was Floyd Mayweather, who earned $300 million in winnings and endorsements combined in 2015. Sharapova and Williams were the only two female athletes to make it into the top 50 earners on that 2015 list.

The female athlete's success is also noteworthy because she is one of very few famous black tennis stars in the world, and she has often discussed overcoming racial barriers on the court and with fans. "I’m a black woman, and I am in a sport that wasn’t really meant for black people," she wrote in a November article for Wired magazine.

Much of Williams' revenue comes from a series of lucrative endorsements with well-known brands, including Beats Electronics, Burlei, Delta Air Lines, IBM, Gatorade and JPMorgan Chase, among others.

Serena Serena Williams, celebrating after winning a point during the Wimbledon Lawn Tennis Championships in 2015, is now the top-paid female athlete in the world. Photo: Getty Images

“There are a number of factors we take into consideration as we’re evaluating potential partnerships. Serena’s excellence on court, her work in the community and her following in pop culture are a few things that set her apart and are complementary to our brand,” Frank Nakano, head of Sports and Entertainment for JPMorgan Chase, told Forbes.

After Sharapova admitted that she failed a drug test in March, the Russian-born tennis star put tens of millions of dollars in endorsements at risk. Nike, Porsche and Swiss watchmaker Tag Heuer suspended endorsement deals days after she admitted to using the recently banned substance Meldonium. Sharapova maintains that she didn’t know the drug had been recently banned and was taking it for a magnesium deficiency.