Mark Zuckerberg Shows Off Shredded Bod In Training Sesh With UFC Stars

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

TMZ Sports has learned ... both Israel Adesanya and Alex Volkanvski flew to Zuck's crib in Northern California following Saturday night's UFC 290 showcase in Vegas -- and almost immediately, they got to work with the Meta honcho on the mats to prep him for a possible tilt with Musk.

The three obviously worked out for a while -- 'cause check out the photos, they were drenched in sweat.

What's even more notable about the pics, though, is Zuckerberg's physique -- the dude is jacked!!

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

Adesanya, meanwhile, was impressed with the billionaire's work ... saying in his own comment on the photos, "No fugazi with Mark 🦈 This is Serious Business‼️"

Zuckerberg and Musk have not yet committed to a fight ... but both seem dead serious about getting after each other in a cage later this year.