Ariana Grande's sexy reggae-pop tune featuring Nicki Minaj is a blatant rip-off of another song, just with their vocals added in ... according to a new suit.
Texan man Christopher R. O'Connor claims "Side To Side" -- Grande's smash hit from her 2016 "Dangerous Woman" album -- is essentially his track called "J5 (T6)" ... but someone from UMG Recordings discovered it and got Ariana and Nicki to copy it.
O'Connor tells us he reached out to UMG about the alleged copyright violation and was instructed to send in a demo ... but the company didn't address his accusation of song stealing.
Here's "J5 (T6)" -- which O'Connor claims was written before "Side To Side." Have a listen and decide for yourself if there's a resemblance.
O'Connor also tells us he believes UMG has found some more of his songs online and used them to produce other copies ... by artists like Mike Shinoda and Taylor Swift.
He's suing UMG -- not Grande or Minaj -- asking for royalties from "Side To Side" (which currently has over a billion views on YouTube) and a song-writing credit.
We reached out to UMG ... no word back so far.