Beyonceu0301's birthday was last week, falling on Labor Day weekend, and since most people were busy -- she seemed ready to party this weekend ... as was the rest of Hollywood.
The stars were out and on the prowl Saturday night ... hitting up a mansion in Bel Air, where Bey and Jay-Z were hosting to celebrate her the big 4-1. It would appear just about anyone who's anyone got an invite -- and they didn't hesitate to take Bey up on her offer to party.
Huge celebs showed up dressed to the nines for this thing -- folks like Drake, Lizzo, Adele, Rich Paul, Jaden Smith, Bella Hadid, Kris Jenner, Kim K, Tristan Thompson, Khloe, MGK/Megan Fox, Lily-Rose Depp, Offset and even Vanessa Bryant.