Huge shakeup at Simon Cowell's new show "X-Factor" -- TMZ has learned singer Cheryl Cole will no longer be a judge ... and will be replaced by ex-"Pussycat Dolls" member Nicole Scherzinger.
It's unclear why Cheryl is out -- but we're told the replacement happened very recently.
Nicole was originally supposed to co-host the show with Steve Jones when it debuts in September -- but now, she'll be sitting on the judge's panel alongside Simon Cowell, Paula Abdul, and LA Reid.
Calls to Cowell's camp have not been returned.
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