Rihanna Rihanna082608_01_X.jpg Awww, it looks like the R&B princess got to have a birthday party after all!

A source tells X17online exclusively that Rihanna rang in her 21st birthday last night at a house in the Hollywood Hills, and the birthday girl and dozens of her pals partied into the wee hours of the morning.

Rihanna's bodyguards handed out autographed shots of the singer and asked folks in the neighborhood to keep her presence on the down low, as they didn't want to attract too much attention to the scene of the soiree.