RIHANNA had a huge party Friday night for her 27th birthday, and sources say her alleged boyfriend LEONARDO DICAPRIO helped put it on. It was held at a private home in Beverly Hills and lasted until 4:00 A.M. the next morning.

Guests included Naomi Campbell, Mick Jagger, Beyoncé, Jay Z, and Russell Simmons. A source says Rihanna and Leo were, quote, "dancing close all night."

(Check out a picture and video from the party. And here's Rihanna's birthday message to herself.)