(TMZ) -  Lil Yachty's crew got into a brawl at SXSW ... with themselves.

TMZ obtained video of Yachty's bodyguard beating down a guy who is part of the rapper's entourage ... or at least he was. The fight went down Friday at the Omni Hotel in downtown Austin.

The clip starts with punches being thrown and Yachty standing nearby and watching the action unfold.

Law enforcement sources told TMZ police responded to a disturbance at the Omni, and say they investigated a fight in the lobby. For what it's worth ... another member of Yachty's crew tried to intervene, but ultimately hotel management broke it up.

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