Steve-O is making UFC history, thanks to heavyweight champ Jon Jones -- 'cause we're pretty sure a UFC belt's never been paired with a hammer to smash someone's ear!!!
Check out the insane clip, if your stomach can handle it -- the "Jackass" star was chilling with Jon in Albuquerque when they came up with the crazy idea for Jon to try to give Steve cauliflower ear.
It's a gnarly deformation of the ear wrestlers and combat fighters commonly get from competition, but Steve-O took a short cut -- laying his right ear under Jon's belt and having Jon literally hammer the belt.