Britney Spears [1] celebrated her 35th birthday [2] surrounded by her fans at 102.7 KIIS FM's Jingle Ball in LA on Friday night. Not only did she deliver an incredible performance of a medley of her hits, including "Slumber Party" and "Womanizer," but the event's host, Ryan Seacrest [3], surprised the singer by coming out on stage with a giant three-tier birthday cake and leading the audience to sing "Happy Birthday."

Later that night, Britney uploaded a video from the show on Instagram [4], writing, "Thank you for the sweet birthday wishes! Had an amazing day. Love you all 💖💖💖 #KIISJingleBall." Lance Bass, who also happened to be at the concert, shared a photo of him and Britney [5] on Instagram on Saturday and captioned it, "It's been a minute since I've spent a birthday with this one! Good to know we still like rips in our jeans. 😜@BritneySpears @MichaelTurchin #BirthdayGirl #JingleBall." It's safe to say that Britney had one hell of a birthday.