A POTUS, a Biebs and a Kardashian walk into a fight -- that's what's going down at UFC 264 in Vegas this weekend ... with a massive list of celebs set to watch Conor McGregor face off against Dustin Poirier!!!
Our UFC sources confirm ... former President Donald Trump is among huge names slated to hit up T-Mobile Arena on Saturday for the fight ... including Justin Bieber, Megan Fox, and Machine Gun Kelly.
Impressive, right?