TMZ Sports broke the story ... 54-year-old Tyson and 51-year-old Jones Jr. are coming out of retirement to put on a massively anticipated 8-round exhibition fight -- and combat sports fans are PUMPED!

But, Foreman -- who had 81 professional bouts against immortal fighters like Muhammad Ali and Joe Frazier -- says he's very concerned about "Iron Mike" and RJJ's well-being.

"There's a time when you gotta worry about your health, but it's a beautiful thing that they would even come out," George says.

"Maybe they can even name a charity or something for the recipient of the funds. I think it's good to come out but its gotta be a fun thing, but I hope one does not hit the other."

FYI, Tyson -- who last fought in 2005 -- told us he's donating a portion of his fight paycheck to charity.

Foreman is admittedly anxious Mike and Roy could be permanently hurt, so we asked him if he'd advise the men to rethink their decision to step back into the squared circle.

"I would just tell them it's really dangerous but when you make up your mind to do something like that, you can't tell them 'don't do it.' They're not gonna hear that. Even me. Big fool like me, back in the day, I only saw what I wanted to see."

George says he totally understands why Mike and Roy want to fight ... and even revealed he attempted to make a third comeback in his mid-50's.

(Of course, George became heavyweight champ for a 2nd time at 45 years old.)

"I was 55 years old. I was in shape and everything," Foreman says, continuing ... "[My wife] says 'you're not going to do anything like that,' I said, 'I'm telling you, you can't tell me what to do. I can still  -- I said don't you believe in me? Look at me, I can still do it!'"