Dana White Says Elon Musk, Mark Zuckerberg 'Dead Serious' About Fighting in UFC

Elon Musk and Mark Zuckerberg are "absolutely deadly serious" about fighting each other in a UFC Octagon and it would be the biggest fight in the history of the world, so says UFC Prez Dana White.

Dana told Harvey and Charles on "TMZ Live" Thursday he's been talking and texting with Mark and Elon Wednesday night and into Thursday, and says both men want to square off in Vegas.

"Talked with Mark and Elon last night, both guys are absolutely dead serious about this," White said.

It all started on Wednesday when Musk responded to a report Zuck was going to launch his own version of Twitter, to which Elon responded, "I'm up for a cage match if he is lol."

The Facebook founder got wind of the tweet, and served up a message of his own, writing ... "Send me location." BTW ... that's code in the world of UFC for, he's really serious.

So, fight on?? People weren't exactly sure if the men were just messing around ... but alas, White says they're not.

As for how big the event could be -- Dana believes it would easily be the most-watched fight ever, saying "The biggest fight of all time was Floyd and Conor, I just think it triples that -- it triples what that did, there's no limit on what that thing can make."

Dana's confident both men are capable of handling themselves. Zuck has been in jiu-jitsu competitions recently, and Elon has done martial arts and told Dana he was involved in "plenty of fights growing up in South Africa."

DW says the cost for Pay-Per-View would be $100 a pop ... it's normally $80 for a UFC fight. Forget about what it would cost to watch it in the arena. Dana expects the fight would gross hundreds of millions of dollars, and the loot would go to charity.

Bottom line ... this is no joke. Mark and Elon are serious, and Dana is determined to make it happen.

You can watch the full interview on "TMZ Live" Thursday.