Japan's Osaka made the announcement just days after lifting her third major title behind closed doors at the US Open in New York, the first Grand Slam tournament possible since the pandemic.
Osaka's corporate sponsors are muted in backing or understanding her campaign against racial injustice in the United States.
On the first day of the US Open, Naomi Osaka came on to court wearing a face mask with the name Breonna Taylor written across it.
Osaka won her third career Grand Slam title after securing a win over Victoria Azarenka in the final of the US Open.
Osaka, of Japanese and Haitian heritage, wore different masks honoring victims of systemic racism and police brutality in the United States in each of the tournament's seven rounds.
Osaka, the fourth seed, overcame her unseeded opponent 1-6, 6-3, 6-3 inside a near-empty Arthur Ashe Stadium at Flushing Meadows.
The match was played with the retractable cover at Arthur Ashe Stadium shut, and rain loudly pelted the roof.
By the time the US Open fortnight is over, Osaka says she hopes to have honored the memory of six other victims of racial injustice.
Karolina Pliskova, the world number three, is the highest-ranked player and top seed going into the second Grand Slam tournament of the year.
World number 78 Sara Sorribes Tormo capitalised on a careless performance from Osaka, who made an astonishing 50 unforced errors in the 15 games.
The 15-year-old American became the youngest player to beat a top-five opponent in a women's tour-level match since Jennifer Capriati did it at 15 in 1991.
Naomi Osaka dealt better with the blustery Melbourne conditions to defeat China's 42nd-ranked Zheng Saisai 6-2, 6-4.
Naomi Osaka, the world's second highest-paid female athlete after Serena Williams, powered through 6-2, 6-4 in 80 minutes.
Osaka had a rollercoaster 2019, winning in Melbourne and topping the world rankings but then ploughing through three coaches.
Osaka held the No. 1 ranking at the end of last January and finished 2019 at No. 3, after withdrawing from the WTA Finals because of a shoulder injury.