That's Logan Paul GOING OFF about how he would wreck Floyd Mayweather if they ever got into a "real" fight ... while insisting he's still down to fight the G.O.A.T. in a boxing ring, too!

Paul was out at Boa Steakhouse in L.A. over the weekend when he was asked if there's been any progress in a possible Logan vs. Floyd boxing match in the near future.

As we previously reported, 43-year-old Mayweather was recently approached with the idea of having an exhibition bout with 25-year-old Paul ... but no deal has been signed.

Paul was tight-lipped about the plans when we saw him back in September, but now he's calling out Floyd publicly ... and talkin' a TON of trash in the process.

"Let me tell you this, if I caught Floyd in a real fight, street fight, whoop his ass! No question," Paul said ... "MMA? Octagon? Whoop his ass!"

"The only place I think Floyd is safe obviously is the boxing ring, but to be honest, I don't give a f*ck! I don't give a f*ck! I would fight Floyd anytime, anywhere, any place. Doesn't f*ckin' matter to me."

Paul continued, "I'm 8 inches taller, I'm 40 pounds heavier, I'm half his age, I'm 2 times as hungry and 10 times as smart. I'm used to beating up people weaker and shorter than he is. I grew up with Jake!"

When asked why Mayweather won't sign the contract, Logan offered up this explanation.

"Bro, think about it. He's got everything to lose, I've got nothing to lose. Mr. Money wants a money fight!? Let's f*ckin go."