Sabalenka shone against four-time grand slam winner Osaka.
"I'm most pleased with how I served and that I managed to put pressure on her," said Sabalenka.
The Belarusian is now the only Grand Slam winner left in the women's and men's singles at Roland Garros.
In the men's singles, both world number one Jannik Sinner and Novak Djokovic were eliminated last week.
Sabalenka has now advanced to at least the quarterfinals in 14 consecutive Grand Slam tournaments and is chasing her first title in Paris. In the quarterfinals, she will face Russian Diana Shnaider.
