Kevin Costner -- Bring MMA to Olympics ... 'Where the Real Tough Guys Exist'

Did you know ... table tennis is an Olympic sport -- and MMA is not?

Well, Kevin Costner ain't happy about it -- telling TMZ Sports he thinks the powers that be should bring the fighting sport to the Olympic games, ASAP!!!!

Costner says MMA has already "established itself as one of the greatest sports out there" ... adding, "I think it's where the real tough guys exist."

BTW, Costner's not the first high-profile dude to call for MMA in the games ... Randy Couture's been banging this drum for years.

#NoDisrespectToPingPong