Mike Tyson vs. Roy Jones Jr. has officially been moved to Nov. 28 -- with another former world champ fighting on the undercard, TMZ Sports has learned.
The fight was originally set to go down on Sept. 12 -- but now, we're told the new date is locked in.
So, why the change to Thanksgiving weekend?
"Changing the date to November 28th will give more people the opportunity to see the biggest comeback in boxing history," Tyson said in a statement.
"This temporary inconvenience will last longer than Roy Jones Jr. He better be ready, I'm coming full force."
The company behind the event, Triller, says the move was made to accommodate a larger audience than originally anticipated.
"Given the enormous interest, the holiday weekend will make this historic battle an even bigger viewing event," the company says ... "marking the first live Pay-Per-View event brought to the world by Triller as the first of the 'Triller Battles' series."
Triller is also officially announcing the addition of new undercard fights ... including Badou Jack vs. Blake McKernan.
Badou Jack is one of Floyd Mayweather's fighters -- he's 22-3-3 and a former world champ in 2 weight classes.
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Jack says he's donating a portion of his fight check to the Badou Jack Foundation to "continue to give kids across the globe a fighting chance in life."