OK, first things first. Happy 27th birthday Britney!

All eyes were on Ms. Spears as she stood in the center of the ring on ABC's "Good Morning America" this morning, where she performed two songs from her brand new album, Circus, which hit stores today in the US!!

Hundreds of fans surrounded the Circus themed stage, with Brit's mom Lynne, father Jamie, brother Bryan, assistant Brett, and choreogtapher/set designer Wade Robson in the audience. Also seated were Spears' two sons, Sean Preston and Jayden Spears, as they watched their mommy put on a show.

The pop princess, donning a black top-hot, looked toned as ever in a pair of tight black leather pants and a belly-baring top as she knocked out the audience with a blazing performance of her forthcoming new single "Circus."

Spears then ditched the top-hot and opted for a red belly-baring number and a pair of black leather knee high boots as she performed her international smash single "Womanizer."

Brit-Brit was then greeted with a large Circus-themed birthday cake and special happy birthday messages from celebrities, including actress Reese Witherspoon, country singer Taylor Swift, and actor Hugh Jackman.

It's official, she's back!

Stream Brit's GMA Birthday bash below:

Earlier yesterday, Britney announced the dates for her upcoming world tour, "The Circus Starring: Britney Spears," with The Pussycat Dolls confirmed to be opening up for the pop princess.

For all the information and to get your tickets, click here!!!

More shots of Brit rocking out GMA below:

Update: In just a few short hours, Britney's "Circus" has hit the #1 spot on the iTunes Top Albums Chart!