Lil Wayne and Birdman‘s war is blowing up in public now — the Cash Money boss dumped a drink on Wayne’s head!

The massive diss went down in Miami’s Club LIV on Sunday night. Weezy was onstage, next to the DJ booth when the drink was hurled from a VIP booth above … where Birdman was standing.

You can’t see it in the video, but sources inside the club tell TMZ … Birdman did it. Also, we’re told Wayne was doing his song, “CoCo — which is basically a diss track against Birdman and Cash Money.

Seems crazy they’d show up in the same club — considering their legal feud — but both came out for a Jim Jones party.

Watch … when the camera goes up to Birdman’s booth, there’s a guy with a look that says … “What? Do something.”

Wayne’s crew didn’t retaliate — but it’s clear. The gloves are off.