Jessica Simpson Is 39 — See Photos From Her Glamorous Birthday Party!

Happy birthday, Jessica Simpson! The singer turned fashion designer turned 39 on Wednesday, and she celebrated in one of the sexiest ways possible: in a leopard bikini! Jessica threw an over-the-top pool party with her closest friends, including CaCee Cobb and stylist Nicole Chavez. "39 is all mine!!!" she captioned a glamorous Instagram shot of herself in jeweled sunglasses, gold hoop earrings, and a leopard beach cover-up.

Jessica's fun-filled bash comes just a day after she excitedly announced that she's releasing her first memoir, which hits shelves in February. "I have been working so hard on it," Jessica wrote on Instagram. "I have opened my heart up in a way I never have before and now I can't wait to share it with the world." In addition to her upcoming book, Jessica and husband Eric Johnson welcomed their third child, a baby girl named Birdie, in March. Birdie now joins their two other adorable kids, 6-year-old son Ace and 7-year-old daughter Maxwell.