Mark Zuckerberg shows off his shredded body in training session with UFC stars

Mark Zuckerberg is clearly taking his potential fight with Elon Musk seriously... he revealed on Tuesday that he is already in training sessions with some of the UFC's biggest stars - and he looks damn good doing it!!

TMZ Sports has learned... Israel Adesanya and Alex Volkanvski flew to Zuck's Northern California hometown after Saturday night's UFC 290 presentation in Vegas - and almost immediately worked with the boss Meta on the mats to prepare him for a possible tilt with Musk.

The three obviously worked for a while - because look at the pictures, they were drenched in sweat.

What's even more remarkable about the photos, however, is Zuckerberg's physique - the dude is screwed!!

The 39-year-old flexed big pecs, chiseled arms and a six-pack in the footage. He also added in a comment on the photos: "It's an honor to train with you!"

Adesanya, meanwhile, was impressed with the billionaire's work...saying in his own comment on the photos, "No fugazi with Mark