Britney Spears will officially become a celebrity judge on Fox's "The X Factor" in a deal reportedly worth $15 million.

Spears will join Simon Cowell and L.A. Reid on the judges' panel, replacing departing judges Paula Abdul and Nicole Scherzinger. Demi Lovato has been rumored to be the next celebrity judge to be named soon.

A source told E! Online, "The contract is signed. There's been a lot of back and forth over the past few weeks as they negotiated the small details, but she's on. It's all completed and Britney is beyond excited."

The source added, "She's ready for this. She can't wait to sit down next to Simon at the judges' table and give this everything she's got. She is excited about showing the world that she can do this, and do this well. This is the perfect next stage in her career. Both Britney and Simon are very excited to work together."