UFC's Junior Dos Santos Says That's Not Him In Violent Nightclub Rampage!

UFC star Junior Dos Santos -- a former heavyweight champ -- claims he's been FALSELY identified as the violent maniac who knocked out several people in a nightclub rampage ... and he's pissed.

The video is insane -- showing a muscular dude dancing in a club on August 19 before another patron accidentally bumps into him. That's when it all goes to hell.

The man in the video explodes -- throwing haymakers at EVERYONE and sleeping dudes left and right. One of the men was knocked out cold and looked to be seriously injured.

The maniac continues brutalizing everyone in his path while onlookers try -- in vain -- to control him.

The security footage was posted online and identifies Junior by his nickname, "Cigano."

But, we spoke with Junior's attorney who is adamant the assailant is NOT her client -- claiming he was in Turks and Caicos with his family at the time and didn't set foot in a nightclub that evening.

We're told Junior's team has already reported the video to YouTube in the hopes of removing Junior's name from the title and description, claiming it's already hurting his reputation.