Naomi Osaka and her coach Wim Fissette have split, with the news announced by Fissette on Instagram.
The pair have enjoyed a successful two-year partnership, notching tournament wins at the 2020 US Open and 2021 Australian Open.
The reason behind the split has not been made public.
Fissette's next move has also not been outlined but he is likely to remain in tennis, having previously coached players including Simona Halep, Victoria Azarenka, Kim Clijsters and Angelique Kerber.
The 42-year-old Belgian coach paid tribute to Osaka in a post on Instagram.
"It has been a privilege to coach Naomi since 2019 and see her grow into the champion she has become," Fissette wrote.
"She has inspired a whole new generation to fall in love with the game and to speak up for what they believe in and it’s been incredible to play a part in that journey.
"Thank you [Naomi]. I wish you all the best and looking forward to my next chapter."
Osaka is currently ranked world No. 38 after missing a number of tournaments over the past year and a half - notably, the 2021 French Open, which she withdrew from due to media commitments and mental health issues.
She most recently played in an opening round loss to Amanda Anisimova at Roland Garros in May but is set to return to the WTA tour in San José next month after battling an Achilles injury.
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Osaka's split with her coach follows her decision to part ways with prominent agency IMG in May before co-founding Evolve alongside her former agent Stuart Duguid.
Last month, Nick Kyrgios was announced as the first player to sign with the Japanese tennis star's new sports agency.
