'Rico Suave' Singer Sues -- I Deserve FOUR MILLION DOLLARS!

The one-hit wonder who sang that catchy "Rico Suave" song back in the '90s claims he's been swindled out of millions of dollars by Lady Gaga's musical director ... this according to a lawsuit obtained by TMZ.

Gerardo Mejia grew up to be a bigshot music executive with Interscope Records -- but according to the suit, filed in L.A. County Superior Court, Gerardo left his gig in 2004 to become a personal manager for an up and coming music stud named Fernando Garibay.

Gerardo definitely has an eye for talent -- because Garibay has been a MASSIVE success, as the musical director for Lady Gaga's "Born This Way" album ... and has also worked with megastars like Britney Spears, Sting and Enrique Iglesias.

But according to the docs, Gerardo claims he never got his commissions for the "lucrative" deal he scored for Garibay back in 2007 ... and now, he wants his revenge in court.

Gerardo is now demanding AT LEAST $4,000,000 for his troubles.