Here's Charles Barkley admitting he hasn't worn a pair of undies since 2008 ... AND NOT REGRETTING IT AT ALL!!!

"I've been 10 years without underwear," Chuck shamelessly said to Jimmy Fallon on Thursday's episode of the 'Tonight Show.'

"And, I feel good about it, Jimmy," he exclaimed!

The question was raised by Barkley's pal and "Inside the NBA" cohost Shaquille O'Neal -- who wanted to confirm a rumor he heard about Chuck's fashion choices below the waist.

The Round Mound of Rebound wasn't shy -- and explained:

"I thought they were unnecessary for space in the house. So, I gathered all my drawers together and had a big ole bonfire."

FYI ... Chuck's packin' a 6-foot-6, 252-pound (ish) frame into those underwear-less pants ... AND the dude lives in freakin' ARIZONA!!!!