It had been rumoured earlier this week that she had decided to quit after learning that Simon Cowell was about to fire her.
"I've made the very difficult decision not to return for another season," Spears said in a statement.
"I had an incredible time doing the show and I love the other judges and I am so proud of my teens but it's time for me to get back in the studio.
"Watching them all do their thing up on that stage every week made me miss performing so much! I can't wait to get back out there and do what I love most."
The popstar added that Fox had been informed of the decision.
Sources have alleged that Spears was on the verge of being dropped from The X Factor USA because of her "boring" feedback and failure to "connect" with contestants, with some apparently claiming she would "barely look at them on stage".
The popstar is currently working on a new studio album, the follow-up to 2011's Femme Fatale, with Jay-Z producer Hit-Boy.
Photo gallery - X Factor USA finals part 2:
Copyright: Fox Ray Mickshaw