Billie Eilish is celebrating a very special birthday ... with Billie's then blonde locks in an updo as she clicked a selfie wearing a black swimsuit and a gold chain. Claudia, meanwhile, was ...

"The second pic made me gasp," referring to her bikini snap, while a third added: "Billie Living HER Life! What a time to be alive!" MORE: Billie Eilish makes surprising revelation about her ...

Billie Eilish was made for writing hits. And she has the awards to show for it, picking up nine Grammys and two Academy Awards all before turning 23. For her latest birthday milestone, Dec. 18 ...