EXCLUSIVE

Birdman is going after Jay Z in court, claiming Jay is a failure at music streaming and is illegally using Lil Wayne to save his business.

Birdman's company, Cash Money, is suing Tidal for streaming songs from Lil Wayne's album 'FWA' ... suing for $50 MILLION. Cash Money claims it has exclusive rights to Wayne's music and Tidal is an illegal intermeddler.

The lawsuit, obtained by TMZ, gets nasty, with Cash Money claiming Jay Z's fledgling company is now resorting to "a desperate and illegal attempt to save their struggling streaming service."

According to the lawsuit, Tidal has claimed Cash Money does not have a exclusive lock on Wayne ... Tidal claims Wayne specifically gave it the right to stream his music, in return for part ownership in the company.

Cash Money begs to differ, and the company quotes portions of its contract with Lil Wayne in the lawsuit. The contract specifically says Wayne does not have the power to license his music to anyone else.