Nicole Richie's Birthday Weekend -- The Bikini Photos

Nicole Richie celebrated her 30th birthday this weekend by jetting to sunny Los Cabos, Mexico with some superstar friends.

Richie was joined by Jessica Simpson, Ashlee Simpson, her boyfriend Vincent Piazza, Samantha Ronson and actress Juliette Lewis -- and all enjoyed some time in the sun in their bikinis by the pool and ocean.

No sighting of Nicole's husband, Joel Madden, or Jessica's fiance, Eric Johnson.

Check out the vacation photos above. Not a bad way to spend a birthday!