Conor McGregor just copped an insanely expensive Rolls Royce Phantom ... with an eye-popping price tag of over $1.3 MILLION!!!

The UFC superstar hit up Instagram to show off the new ride this week, and it's sweeeeeeeet!

As for the specs of the whip, we're told the black Rolls-Royce Phantom VIII Diamond Edition features a V12 engine with a whopping 571 horsepower and a max speed of 155 mph.

In fact, the Phantom goes 0-60 in just over 5 seconds ... super fast for such a big and heavy vehicle.

The interior of the RR is decked out in all-black ... with a bunch of race-inspired features like sport pedals and a steering wheel. The RR also has a special lighting kit, in addition to a gang of other features.

The exterior of the Phantom -- customized by Mansory -- features big 24" black-painted wheels, a carbon fiber rear bumper, a roof and rear spoiler, and an illuminated ambient grill. It's also got a sports exhaust system, and the suspension has been lowered.

All those features don't come cheap ... we're told the car is worth over $1.3 million!

But, Conor loves nice things (see his Lambo yacht), and he's got the money.

The UFC superstar has earned hundreds of millions of dollars in his career ... cashing big paychecks from his fights, as well as his lucrative business ventures away from the Octagon.

The purchase comes amid McGregor's foray into politics ... with The Notorious recently announcing his intent to run for president of Ireland.