"Hey guys, I am out of the hospital. I was in there for 3 days. COVID hit me really hard," ODLH said via social media, adding, "I was in the best shape of my life and I really can't wait to get back in the ring."

Of course, Oscar was scheduled to fight Vitor Belfort on September 11 ... but was forced out of the event when he contracted the virus.

It wasn't just a matter of Oscar being positive ... he was hit hard by the virus, forcing him to go to the hospital on Friday.

Oscar managed to film a video the same day from his hospital bed ... and it was clear he was in bad shape.

However, the Hall of Famer bounced back quick ... and is clearly on the med.

Unfortunately, De La Hoya's still out of his Saturday night fight with Belfort ... and fellow legend, Evander Holyfield has stepped in to fight the MMA legend.

If that wasn't enough ... former President Donald Trump -- who doesn't see eye-to-eye with ODLH -- will be doing commentary for the fight.

Bottom line, despite the setback, Oscar made it clear he still intends to return to the ring after a decade-plus layoff ... and he closed out his health update with a big shout-out to his millions of fans.