USA Wrestling Legend -- Thank God Wrestling is Back in Olympics!

The International Olympic Committee just announced wrestling WON'T be axed from the 2020 Tokyo Games after all ... and one of the biggest stars in the sport couldn't be more thrilled.

TMZ spoke with Rulon Gardner -- former "Biggest Loser" contestant and gold medal winner at the 2000 Sydney Games -- who tells us the IOC's ruling made his day.

Rulon says he still can't believe the sport was ever on the chopping block to begin with ... but he's pumped "wrestling will showcase it's greatness to the world once again."

As for the other sports nixed from the 2020 Games, like squash, they're still out ... because no one cares about squash.