Simone Biles will not be defending her gold medal in the all-around final at the Tokyo Games — the Olympics superstar has backed out of the competition to continue to focus on her mental health.

24-year-old Biles — who withdrew from the team finals on Tuesday — underwent further medical evaluation following the event … and it was determined it was best she sat out Thursday’s finals, USA Gymnastics said in a statement.

Biles was the heavy favorite to win the event … which would have secured the 5th gold medal of her career.

It may not be the end of Biles’ Olympic run, however — there’s still a chance she returns to compete in the individual events next week … but the team says it all depends on the results of her daily evaluations.

“We wholeheartedly support Simone’s decision and applaud her bravery in prioritizing her well-being,” USAG said. “Her courage shows, yet again, why she is a role model for so many.”

Biles absolutely crushed the competition at the 2016 Rio Games … posting a 62.366 score, with teammate Aly Raisman taking silver with a 60.607.

Jade Carey — who placed 9th in qualifiers — will be Biles’ replacement.