The previous record was Maria Sharapova in 2015 with $29.7 million.
The 22-year-old Asian star, a two-time Grand Slam champion, edged USA rival Serena Williams by $1.4 million in prize money and endorsement income over the past year.
Sports business professor David Carter said that Osaka's "great back story" - her family moved from Japan to NY when she was three, where her father tried to emulate Williams' father, Richard, by teaching her tennis from a young age - was an integral part of her allure for advertisers.
"Combine that with being youthful and bicultural - two attributes that help her resonate with younger, global audiences - and the result is the emergence of a global sports marketing icon".More news: Megan Fox in Machine Gun Kelly's music video
Now she is No. 1 on another list: top-earning female athlete. The full list is set to be released next week.
Williams had annual incomes from $18 million to $29 million and has collected almost $300 million, much of it in endorsement deals. The 38-year-old, 23-time Grand Slam victor did just fine, earning $36 million for the second-biggest payday ever for a female athlete.
The pair met in the 2018 US Open final with Osaka winning her first Grand Slam title in a highly controversial match in which Williams was given three code violations by the umpire.
With $37.4 million in prize money and endorsements over the past year, Osaka is the highest-paid female athlete ever.More news: Federal government releases guidelines on nursing home visitation
She has won about $14.5 million in career prize money, according to the WTA, a little less than half of which was earned in 2019.
According to Forbes, Osaka has 15 endorsement deals with partners Nike, Nissan, beauty brand Shiseido and racket-manufacturer Yonex each paying her seven figures. Her deal with Nike is worth more than $10 million annually and runs through 2025.
Since Forbes began tracking women athletes' income in 1990, tennis players have topped the annual list every year.More news: Palestinians Stop Sharing Intelligence With CIA Over West Bank Land Grab Plans