Paris Hilton is officially persona non grata in Japan because of that whole cocaine thing.

Japanese Immigration officials denied Paris entry into their county because of her guilty plea to cocaine possession this week.

Japan frowns on people who get convicted of drug offenses, so Paris -- seen above at the airport a few hours ago -- is on her way back to the US of A.

Before getting the boot, Hilton was detained at the airport yesterday for more than 6 hours.

A rep for Hilton says "Paris is very disappointed and fought hard to keep her business commitments and see her fans, but she is forced to postpone her commitments in Asia. Paris understands and respects the rules and laws of the immigration authorities in Japan and fully wishes to cooperate with them. Paris looks forward to returning in the future to a country she loves and has been coming to for the past 10 years.”