Slap Fighting Champ Says Sport Is The New MMA

Barbaric, overly violent ... just some of the words used to describe slap fighting, much like MMA back in the day. But, cage fighting exploded in popularity, and now an undefeated slap fighting champ tells us he believes the sport is about to blow up.

"For us to be doing this at the Arnold, it kind of speaks volumes to where the sport is gonna be in the future, and I believe it's gonna be a thing how like the MMA scene, and the UFC started and was looked at as a brutal sport. Slap fighting is just that, but a little less brutal," Koa "Da Crazy Hawaiian" Viernes, an undefeated slap fighter told TMZ Sports.

Koa -- a 6'2", 378 lb., 9-0 slap fighter from Hawaii -- is competing in the Slap Fighting Championship Super Heavyweight World Championship this Saturday at the Arnold Sports Festival.

The comp is being hosted by Arnold Schwarzenegger AND Logan Paul ... and will pit Koa against fellow undefeated champ (16-0), Dawid "Zales" Zalewski.

We asked Koa -- who grew up boxing -- what it feels like to be slapped ... and he says it hurts way more than being punched.

"If you've gotten punched in the face, it's completely different. When you get slapped, your fingers ricochet off the skin, the whole open hand, it hurts a lot more."

FYI, back in the mid and late '90s, MMA promoters had nearly an impossible job when it came to finding a venue to hold their events. In fact, MMA wasn't legal in all 50 states until 2016, when New York reversed a ban that disallowed mixed martial arts competition.

Now, the UFC -- and MMA as a whole -- is insanely popular ... and promotions routinely host hugely popular events at some of the biggest and most famous arenas around the world.

Can Slap Fighting become the next UFC? Koa thinks so ... and we're certainly not gonna tell him no.