Jan 13 (Reuters) - Japan"s Naomi Osaka, a four-times Grand Slam tennis champion who has helped raise awareness of mental health issues in sport, is the world"s highest-paid female athlete, according to a list published by business magazine Forbes on Thursday. Osaka raked in $57.3 million in prize money and endorsements over the last year, nearly all of which came from an endorsement portfolio that has added more than 10 brand partners over the last year and a half. The list was published after a year in which Osaka withdrew from the French Open to focus on her mental health amid a public row over mandatory press conferences at the Grand Slam, saying they took too great a toll on her mental wellbeing. Fellow tennis players Serena Williams (45.9 million) and older sister Venus ($11.3 million) were next on the list. American gymnast Simone Biles ($10.1 million) and Spanish tennis player Garbine Muguruza ($8.8 million) rounded out the top five. Tennis players made up five of the list"s 10 spots, which Forbes said marked the sport"s lowest tally in more than a decade and a dramatic change from 2019 when it claimed all 10. Collectively, the 10 highest-paid female athletes earned a total of $166.6 million, which Forbes said was a 23% increase over its 2020 list. South Korean golfer Ko Jin-young ($7.5 million), Indian badminton player P.V. Sindhu ($7.2 million), world number one tennis player Ash Barty ($6.9 million), golfer Nelly Korda ($5.9 million) and basketball player Candace Parker ($5.7 million) were the other athletes in the top 10.