First Photos of Leonardo DiCaprio & Rihanna together

Rihanna and Leo DiCaprio should be a perfect match -- neither's into settling down with one person for too long -- but now that they're banging ... one of them is way more committed than the other.

We got pics of RiRi and Leo getting cozy recently at her birthday party -- which he helped organize -- and sources at the bash tell us one thing was clear ... Rihanna's the clingy one.