Paris Hilton -- Bikini PDA with NEW Mystery Man

Stop us if you've heard this one before ... Paris Hilton's hookin' up with a new guy ... and it was all caught on film.

Paris and her new flavor of the month got pretty hands on with each other during a trip to the beach this weekend in France ... rubbing on each other ... and splashing around in the ocean.

Sources tell us ... the mystery man is a "successful businessman from Europe" ... and he and Paris have been friends for years.