T.I. vs. Floyd Mayweather Jr. -- Brawl Erupts on Vegas Strip [VIDEO]

T.I. took a swing at Floyd Mayweather Jr. and it caused a chair-tossing brawl in the Fatburger on the Vegas Strip early Sunday morning ... TMZ has learned ... and we've obtained multiple videos.

According to several witnesses ... Floyd was eating inside the restaurant when T.I. walked up and started jawing at Floyd.

It's unclear what caused the beef, but we're told T.I. swung at Floyd ... their giant bodyguards jumped in to separate them ... and then the all out melee began.

At one point you hear Floyd telling at T.I., "control your bitch."

Las Vegas PD arrived just as Floyd was leaving and we're told T.I. was already gone.

Police confirm a Fatburger employee was slashed during the fight, but he refused treatment and did not want to cooperate with investigating officers. In other words ... no snitching.

A rep for T.I. had no comment about the fight.

Less than a month ago, T.I. and Game were in the middle of a near riot with LAPD officers outside Supperclub.