Bruno Mars Sued Over Hit 'Uptown Funk'

Bruno Mars' monster hit "Uptown Funk" is a thinly-veiled replica of a groovy tune back in the day ... and now the OG band is out for blood in court.

Mars and "Uptown Funk" producer Mark Ronson are among many names listed in a lawsuit filed by members from the music group, Collage. The band released a single in 1983 called "Young Girls" and claim Bruno's Billboard #1 is a dead-on copy in rhythm, harmony, melody and structure.

It's interesting -- Collage claims Ronson and Mars have been big fans of Minneapolis/1980s electro-funk soul ... of which Collage was a part, along with Prince and others. The suit claims there's reason to believe Ronson and Mars have heard and been influenced by "Young Girls."

The stakes are enormous. "Uptown Funk" is Mars' biggest song to date ... selling more than 6.1 million copies. It's the second-longest number-one hit single in Billboard history, and makes the label alone a reported $100k a week via streaming on Spotify.

Collage -- only has one living member -- but he's alive and kicking ... demanding a cut of the profits and a stop to "Uptown Funk."