UFC's Rashad Evans Ref For Blac Chyna Vs. Magen Fight

UFC legend Rashad Evans will be in the ring next month ... not to fight, but to serve as referee in the celebrity boxing match between Blac Chyna and Alysia Magen.

The mixed martial artist -- who was inducted into the UFC Hall of Fame in 2019 -- made the IG announcement on Tuesday with a clip of Chyna and Magen's first face-off ... where things got a little heated.

"I'll be ref' at this event," RE said with a bunch of fire emojis.

The bout will go down at the Charles Dodge Center in Pembroke Pines, FL on June 11 ... and the winner between Chyna and the Air Force vet will take home the Women's Celebrity Boxing title.

And there's a good cause ... Chyna says the money she raises will go to a…