The biggest UFC fight of all time might just have the biggest celebrity guest list of all time -- with huge stars slated to be Octagonside when Conor McGregor takes on Khabib Nurmagomedov at UFC 229!
We're told Hollywood titans like Chris Pratt and Mel Gibson will be there alongside business moguls like Robert Kraft and Elon Musk.
Other names expected to be at the October 6 fight ... Rory McIlroy, Matt Damon, Anthony Kiedis, Megan Fox, Under Armour CEO Kevin Plank, Joel Kinnaman and Mark Consuelos.
We also got Mike Tyson out on Monday -- and he told us he'll be at the fight too!
Of course, Mike is tight with UFC honcho Dana White ... and he's become a big MMA fan over the years.
Tickets for the fight are getting super pricey -- the cheapest seats on StubHub are going for $650 a pop ... and the good seats are running up to $27,000!!!!!