The theme of the night was "Rei Kawakubo/Comme des Garçons: Art Of The In-Between," honoring the bold, architectural creations of Comme des Garçons designer Rei Kawakubo, and Katy Perry gave her best take on the motif in a bright red Maison Margiela 'Artisanal' dress designed by John Galliano, which she paired with a silk veil, intricate "Witness" headpiece and red leather heeled boots.
Veteran Blake Lively returned to the soiree for the eighth time, proving her style just keeps getting better year after year. The Shallows star sported a plunging gold Versace gown, which featured gorgeous ombre blue feathers cascading down the train. Of course her look wouldn't be complete without some bling -- accessories from Lorraine Schwartz and Ofira Jewels!
Lily Collins opted for a more edgy getup, contrasting her dark, gothic makeup and black bob with a light pink tulle skirt by Giambattista Valli and diamond cluster earrings from Tiffany & Co.
Click through the slideshow below to see 10 more must-see looks from fashion's biggest night!