That very well could be a reality for Logan Paul ... 'cause Iron Mike says he's now down to box the YouTube star -- claiming the fight could earn the two a fortune!!

Tyson revealed on his latest episode of "Hotboxin' With Mike Tyson" that he'd have zero issues stepping into the ring with either Logan or Jake Paul ... adding the scrap could net a $100 million payday.

"Hell yeah," Tyson said when rapper Freddie Gibbs asked if he'd box the two YouTube stars. "That would be a lot of money."

Tyson seems to think boxing Logan would make more sense than fighting Jake ... considering the elder Paul bro is a bit heavier.

As for if Logan would do it ... Tyson certainly thinks so -- telling Gibbs, "For $100 million bucks, they'd do anything. They don't care about getting beat up."

Tyson -- who's coming off a great performance against Roy Jones Jr. -- had previously told us he was eyeing Lennox Lewis for his next bout.

But, if Logan's down ... seems Tyson would have no problem moving on to that tilt.