Cowell quit the original version of the singing show in 2011 to concentrate on launching the series in America, working alongside stars including Britney Spears and Demi Lovato.
Cowell is now heading back to the panel to retake the reins for the next series following the departure of judges Gary Barlow and Sharon Osbourne.
A source tellsThe Sun: "His return has been up in the air for some time - and ITV chiefs have been desperate for confirmation... But now he has confirmed he is back for good."
Cowell is rumoured to be courting another former X Factor judge Cheryl Cole for a seat on the panel.
The music mogul previously fell out with the Girls Aloud star after transferring her from the British version to the American show and then dismissing her shortly after filming began.