Happy Birthday Britney Spears: See Her Best Onstage Pictures

Britney Spears turns 31 today! The singer has brought plenty of hotness since hitting the scene in 1999, including endless amounts of ab-baring ensembles and multiple envelope-pushing dance moves. Britney's new role as a US X-Factor judge and mentor has her hitting the stage in a different way, but her star presence and sex appeal is hot as ever. From sexy schoolgirl to circus ringleader to full-blown femme fatale, we're celebrating Britney's big day with a look back at her steamiest stage moments. Click through to see them all now!