Khloe Kardashian and rapper boyfriend French Montana are all about the PDA.

The two were "all over each other" during a recent double date with Khloe's sister, Kourtney Kardashian, and Kourt's boyfriend, Scott Disick, at 75 Main in Southampton, a witness told us.

Khloe and French were "acting like two honeymooners, kissing in public," the spy added.

We're told Disick left dinner early because of the smoochfest.

The Kardashians are out east this summer filming the reality show "Kourtney and Khloe Take the Hamptons" for E!.