Naomi Osaka is a Japanese professional tennis player. She is the first tennis player from Japan to win a Grand Slam singles tournament, defeating Serena Williams in the final of the 2018 US Open. Osaka has reached a career-high world ranking of No. 7. She is of mixed Haitian and Japanese heritage, and holds dual citizenship in Japan and the United States. As Ōsaka has dual Japanese and American citizenship, her father made the decision to register her with the Japan Tennis Association when she began her career. She turned pro in September 2013. She made her main-draw WTA tour debut at the 2014 Bank of the West Classic, after defeating Alla Kudryavtseva and Petra Martić in qualifying.