Happy birthday, Blue Ivy! The four-year-old celebrated not once, but twice last week ... and she's only four!

Beyonce and Jay Z threw a party for the little tyke at Duff's Cake Mix in West Hollywood, on Sunday, which was preceded by a blowout bash at a private Beverly Hills residence, on Saturday. Hey, why not celebrate for the entire weekend!

Blue Ivy invited celebritots like Ellen Pompeo and Chris Ivery's daughter Stella Luna, Chris Martin and Gwyneth Paltrow's kids Apple and Moses and Destiny's Child singer Kelly Rowland's son Titan.

A fun time was had by all -- no doubt, TONS of gifts were given -- and the little ones all went home with sticky fingers and a sugar rush. Yay!