Paris Hilton and Kim Kardashian both looked drop dead gorgeous while partying in Cannes ... and they were on the same yacht!

The sexy reality stars partied together on P. Diddy's private yacht in the south of France. Ooh la la!

Kim cruised to Cannes with her new beau Kanye West who is debuting a short art film Cruel Summer at the festival.

As for Paris ... she's enjoying a good party. Loves it!