There are a few VIPs coming to the UFC showdown between Conor McGregor and Dustin Poirier tonight in Vegas, including Justin Bieber and Mel Gibson.

UFC boss Dana White says that former President Donald Trump is also coming, and that he's going to be front and center at the side of the Octagon during the whole fight.

Dana White says former President Donald Trump won't be able to hide from the spotlight at UFC 264, because he'll be right next to the Octagon ... where fans can loudly cheer and jeer him.

The UFC honcho joined us Friday on "TMZ Live" to pump up Conor McGregor and Dustin Poirier's third fight ... and, in the process, he settled a debate about where Trump will sit Saturday night in Vegas. It's the first major sporting event Trump's attending since leaving the White House -- and with all that's happened since he lost the election, it's a good bet (even in Vegas) the ex-prez will hear plenty of boos.

Dana, a longtime Trump supporter, says his pal isn't one to shy away from any heckling.

As Dana tells us ... Trump "don't care, he's not that guy, he's not hiding in a box somewhere, that's not his style." Instead, he says Trump will sit right behind him.

No doubt he'll be flanked on all sides by Secret Service, and Dana says agents have been sweeping T-Mobile Arena for a few days now to ensure Trump's safety.

If you're a red-blooded American, you have to at least appreciate that we had a president who doesn't just take photo ops in fancy buildings, but watches two MMA stars beat the crud out of each other from the front row!

Now if you excuse me, I need to get my popcorn ready. God bless America.