Bar Refaeli -- Leonardo DiCaprio Should Bang Rihanna ... And If He Doesn't, I Will!

Bar Refaeli is giving her ex-bf Leonardo DiCaprio the green light (not that he needs it) when it comes to hooking up with Rihanna ... because, well ... LOOK AT HER!

We asked the supermodel about what our sources saw go down at the Playboy Mansion Saturday night -- Leo and RiRi getting very close and even kissing -- and she didn't hold back a bit.

If you were expecting a jealous ex-gf response, forget it -- in fact, Bar sounds like she might be down for a sesh with Rihanna too. Or maybe that's just our wishful thinking.