Celebs ventured to Vegas this weekend to celebrate birthdays, anniversaries, and fashion!

Paris Hilton launched her Sunglasses line at The Hard Rock Hotel Casino, while the Simpson sisters partied it up poolside at the MGM Grand Resort and Casino for Ash’s birthday.

Who got dressed up for Sin City?

PHOTOS: See Paris, Amanda Bynes, Christina Milian, Jessica Simpson, Ashlee Simpson-Wentz, Pete Wentz, Jamie Kennedy, Jennifer Love Hewitt, Benicio Del Toro, and Diddy party in Vegas!