Naomi Osaka Training During Pregnancy, 'Outside But Barely'

Naomi Osaka wasn't lying when she said she would be back for the 2024 Australian Open ... 'cause the tennis superstar looks like she's preppin' for it already -- during her pregnancy!!

The 4-time Grand Slam singles champ shared three Instagram videos of her workout on Monday, a month after she revealed to the world that she was pregnant.

You can see Osaka hasn't lost a step as the 25-year-old shows her powerful backhand on the tennis court. She also had a sweat sesh on the beach -- all while carrying a baby in her belly!!!

"Outside but barely," Osaka said in the caption.

Osaka's fans loved what they were seeing ... and applauded her for keeping up with her routine during pregnancy.

One of the comments said "Huge props!! Being active while pregnant is THE MOST exhausting. 👏🏼👏🏼👏🏼" ... while another fan said, "look at you gooo 🔥🔥 they aren’t ready for 2024 Naomi."

Remember, Osaka said she would not be competing this year since she's expecting her first child with Cordae ... but plans to return for the 2024 Australian Open.

"I know that I have so much to look forward to in the future," Osaka said when she broke the news.