According to a story posted Friday by Forbes, Osaka earned about $37.4 million from endorsements and prize money between June 1, 2019, and June 1, 2020. She racked up $1.4 million more than Williams ($36 million), who was the world's top-paid female athlete each of the last four years.
Forbes said Osaka's total was a new one-year record for a female athlete, topping the previous mark of $29.7 million set by Maria Sharapova in 2015.
Osaka ranks No. 29 overall on Forbes' annual list of the 100 highest-paid athletes, while Williams is No. 33. According to the publication, the full 2020 list is set to be revealed next week.
Osaka, who was born in Japan and moved to the United States when she was three, beat Williams in the 2018 U.S. Open final and then captured the 2019 Australian Open title. Her victories allowed her to become the first player from Asia to be No. 1 in the men's or women's tennis rankings.
Osaka has earned about $14.6 million in career prize money, according to the WTA, a little under half of which was made last year.