KID CUDI GETS KICKED OFF LADY GAGA'S TOUR AFTER HE PUNCHES A FAN IN THE FACE!

Kid Cudi -- the guy who sings that "Day 'N Nite" song -- has been officially dropped from the Lady Gaga tour in the wake of a brutal fan-punching incident.
Sources at Interscope Records confirm the rapper is "no longer" with the tour -- but wouldn't say if the decision had anything to do with YouTube footage showing Cudi punching fans in the front row of a concert in Vancouver this past weekend.

We're told Cudi will be replaced on the Gaga tour by Jason Derulo -- the guy who sings "Whatcha Say."

No comment from Lady Gaga's camp.