A man in Australia was forced to put up his dukes against a buff kangaroo that was holding his dog hostage ... catching the whole thing on camera.
The down-under beatdown took place between the 'roo and Mildura resident Mick Moloney ... who took a swing at the animal, and got knocked in return -- his camera took a tumble into the water, but his dog was safe from the scary situation.
He says it was pretty strong -- but he slapped the marsupial across the head and got into a tussle in the water. Mick admits it looked like it was gonna kick him, too ... but he splashed some water in its face while he bolted to the shore where his dog was safe.
BTW, Mick is a mixed martial arts and Brazilian jiu-jitsu instructor ... but claims people are already asking him when he'll start teaching "roo-jitsu."