Rihanna, Frank Ocean, Big Sean, Cassie, & Diddy Celebrate GQ's 'Men of the Year'

Rihanna celebrated her GQ “Men of the Year” cover at a star-studded bash in Hollywood last night. The “Diamonds” singer, who was named “Obsession of the Year” by the men’s magazine, stole the show in a slinky red Calvin Klein mini, toasting with her fellow honorees Ben Affleck and Channing Tatum.

Big Sean kept it player in a one-of-one Katie Eary shirt and red adidas sneakers, Kid Cudi and Ne-Yo looked fresh out of the pages of GQ, and even the elusive (and tipsy) Frank Ocean came out to party with RiRi at Chateau Marmont. Jamie Foxx was snapped grabbing Rihanna’s digits, while Cassie snuggled up with her man Diddy in VIP.

Check out more pics from the glamorous affair below.