Selena Gomez Parties in Hollywood for Her 21st Birthday, Stops at Julianne Hough’s Bday Bash [Pictures]

Selena Gomez literally just turned 21 and she is already partying like an old pro! The 'Come & Get It' songstress was first spotted at Julianne Hough's '20s-themed, 25th birthday bash on Saturday night with actress Lily Collins. Then, Gomez and Collins headed to the Roosevelt Hotel for her own birthday festivities!

Sel seemed to have a lot of fun at Hough's party, which included a photo booth. Gomez even escaped the shindig sporting a pair of devil horns and a boa as accessories to her sheer little black dress. We say you walk the red carpet with those sometime, Selena!

Selena then left Hough's party for the Roosevelt Hotel in Hollywood, where she could start her very own birthday celebration in style! Still wearing her devil horns, she was surrounded by her friends who presented her with a super cute, cheetah-printed cake.

We wish Selena the happiest of 21st birthdays, as well. We just hope she isn't hungover!

Selena looking gorgeous (and quite devilish) about to blow out the candles on her 21st birthday cake!

Selena'z birthday cake was so freakin' cute! We love the cheetah print with gold accents. Note: Justin Bieber was not there to celebrate, but he was on her cake!

C'mon paps! Let a girl have her 21st birthday in peace!