Kanye West raps new song for girlfriend Kim Kardashian

Kim Kardashian is a "perfect bitch" - well, according to her boyfriend Kanye West.

The rapper confirmed Tuesday that his new tune "Perfect Bitch" was penned with his reality-star GF in mind.

"I wrote the song Perfect Bitch about Kim," he tweeted.

West made an unscheduled debut of the track, which is off his upcoming unreleased album "Cruel Summer," on Friday night at PH-D Rooftop Lounge at the Dream Downtown.

West was just hanging out at the club when he unexpectedly jumped into the DJ booth and played samples of his yet-to-be-released tunes - including his song for Kardashian - to an unsuspecting crowd.

Needless to say, the packed room - which included West's pals Leonardo DiCaprio and girlfriend Erin Heatherton - were "stunned" to see West get up and perform, a witness told us.

"He danced and lip-synched to pieces from his own tracks as he played segments off his own iTunes library," the witness said.