Mike Tyson ain't the only heavyweight training for a comeback -- Evander Holyfield tells TMZ Sports he's gearing up for another fight at 57 years old!
"The Champ is back," Holyfield tells us ... "I’d like to announce that I will be making a comeback to the ring."
"I will be fighting in exhibition matches for a great cause."
Holyfield -- who hasn't had a sanctioned fight in 9 years -- says the goal is to raise money for the #Unite4OurFight campaign which "aims to provide students the resources they need for emotional development and education."
We know what you're thinking ... WHO IS THE OPPONENT?
Evander's team hasn't announced that yet -- but we're all thinking the same thing ... Holyfield vs. Tyson 3???
As we previously reported, 53-year-old Tyson has been training again and wants to take exhibition fights to raise money for charities near and dear to his heart as well ... but there's no official deal yet.
Of course, Tyson and Holyfield had issues over the years after Mike bit off Evander's ear during a 1997 fight -- but Tyson has apologized and they've actually become friends.
So, could there be a 3rd scrap if all the money would go to charity? Don't rule it out.
Holyfield was 44-10-2 as a pro -- with TWO victories over Mike Tyson. He's widely considered one of the greatest heavyweight fighters of all time.