Lil B Jumped and Robbed at Rolling Loud Festival

Lil B left the Rolling Loud Festival with a few battle scars after allegedly getting jumped ... also minus thousands of dollars in equipment and cash after his bag was stolen.

Based God had been backstage before his Saturday evening set at the Mountain View, CA fest when he says rapper A Boogie wit da Hoodie and his posse jumped him.

Lil B claims during the fight, someone -- not A Boogie -- skedaddled with his bag which had laptops, a camera, and a ton of cash. Our Lil B sources say in all $45k worth of stuff was taken.

Lil B had to cancel his set since he didn't have the gear necessary to perform.

Cops tell us they don't have a suspect.

Warning: Footage of the fight ain't for the faint-hearted.