UFC Hall of Famer Stephan Bonnar is back and ready to BRING THE PAIN -- in a pro wrestling ring!
Bonnar's been out of the fight game for a few years ... but The American Psycho told TMZ Sports he and Phil Baroni (another MMA great) are about to lay the smackdown in the squared circle.
"The Real Shooters (Bonnar and Baroni's tag-team) are gonna come put a hurting on you," Bonnar said. "I really enjoy inflicting pain on people."
Bonnar's first match is at a bowling alley .