MMA hotshot JON "BONES" JONES had a hell of a day on Saturday.  That night, he DESTROYED Mauricio "Shogun" Rua... for the UFC Light Heavyweight Title at "UFC 128" in Newark, New Jersey.

But just hours before that, he helped subdue a MUGGER.

Jones was preparing for the fight by meditating at a park in Paterson, New Jersey, when he heard a woman scream, "I've been robbed!"

Jones chased the guy and took him down... and he and his coach subdued him until police showed up.

Jones later Tweeted, quote, "I caught him... Coach Jackson finished him... It feels so good to help others.  It gives me power and energy."

He also posted a picture that his driver took of the incident. (Check it out... that's bones in the white sweatshirt.)

(TMZ claims Jones subdued the guy with a "figure-four leglock"... which is probably complete B.S. and crappy reporting because those clowns still fantasize about the Von Erichs.  The figure-four is not an MMA maneuver.  It's a pro wrestling move...)

(And it's one of the many things in pro wrestling that you really can't do to a guy unless he's LETTING you do it.)

(Shut Up!)