Jennifer Lopez [1] owned the red carpet on Saturday — and it's not just because it was her birthday celebration. Just one day after turning 46 years old, Jennifer made a grand entrance at 1OAK Southampton in Southampton, NY. The actress and singer struck sexy poses in a black cutout dress that revealed her flawless physique. Once inside the event, Jennifer hung out at the DJ booth and reportedly hit the dance floor with Casper Smart [2], her on-again, off-again boyfriend. This isn't the first time the duo has been spotted together in the Hamptons this Summer — they shared a cute day with Casper's dog [3] earlier in July. Keep reading to see how Jennifer celebrated her birthday, and then take a trip down memory lane with a look at her sexiest moments [4].