The 'Oops I Did It Again' singer is a proud mum to boys Sean Preston and Jayden James, who were born pretty much exactly one year apart.
Sean Preston turned nine on 14 September, while Jayden reached eight years old on 12 September.
Their dad is Britney's ex-husband Kevin Federline.
Britney shared a snap from her boys' skateboard-themed birthday party to Twitter, captioning it: "Happy birthday to my two little baby boys. They are growing up too fast!!"
We agree! It feels like only yesterday they were tiny babies!
Britney, 32, celebrated with her boys shortly after performing her final Las Vegas concert for a while. Her Piece of Me show at the Planet Hollywood Resort and Casino is on a break until October.
As well as working in Vegas, the singer recently unveiled her new underwear range called The Intimate Britney Spears Collection.
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!