Rampage Jackson Tells Shannon Briggs He's Going To 'F*** Him Up'

Quinton "Rampage" Jackson wants all the smoke -- the mixed martial artist tells TMZ Sports he's dead serious about fighting Shannon Briggs ... and when he does, "he's gonna f*** him up."

"That guy's a f***ing a**hole," Jackson told us this week. "I want to box and I think that his old ass would be a perfect match to be my first boxing match."

"I'ma f*** him up. I'm sick of that guy. All he does is troll me. Imma f*** him up."

Rampage didn't stop there ... "He think I'm playing with him. He think it's all fun and games. That man 50 years old. He too old to be acting like that," he continued.

Jackson says his desire to clash with the former heavyweight champ came after Briggs called him out following his last loss.

"I told him I wanted to have a boxing match and Shannon agreed to get in there with me," Jackson said. "We putting MMA fans vs. boxing fans."

The feud between Jackson and Briggs ain't new -- last month, they got into a shoving match at a Triad Combat weigh-in (the two were captains of opposite teams) ... an event that pitted MMA fighters against professional boxers.

Jackson tells us that any clash he has with Briggs will be bigger than just pride and ego ... saying that he's gonna show the world that MMA fighters are the best.

"I'm coming to get that respect," Rampage said. "You boxers, y'all don't respect us. Better put some respect on my name."

We might not have to wait much longer to see the former champs lock horns ... 'cause Rampage also told us that we could see the highly anticipated bout sometime in the new year.