Sean "P. Diddy" Combs is under investigation in Los Angeles for allegedly slugging a guy at a post Oscar party.

TMZ.blog is reporting that Diddy was celebrating the Academy Awards at the Roosevelt Hotel in Hollywood when he and the boys met a lady.  The problem started when "the lady's" boyfriend, Gerard Rechnitzer, came back from the toilet to find her surrounded by Diddy's posse.  He wanted to leave, but since her drunk ass was chillin' with Diddy - she didn't want to budge! 

Her boyfriend insisted that she go, and when he wouldn't give up -- Diddy knocked him right in the face. 

The LAPD evidently has a list of witness who saw it all!  Could Diddy be charged with assault and battery?