The exciting news was announced on the show's official Twitter page, with the first post reading, "Fifth Judge? #fifthjudge," alongside a photo of the date when fans will be enlightened.
"Find out who (or what) the #fifthjudge is on Friday...," read the second cryptic tweet.
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Fans have started speculating which celebrity could be joining the panel, but this is the first time the X Factor has mentioned another possible addition.
All focus up till now has been on Sharon returning as the fourth judge, in the place of Tulisa.
The rock queen excited fans with the news of her comeback, and it seems the judges have more than embraced her return and "outrageous" behaviour.
"It's great to have her back," said Gary, speaking at an X Factor event. "We have the queen with us this year and it does feel like we're in the room with royalty. Every day it's mad Sharon."
"Mrs O's pretty outrageous," said Nicole. "She brings more outrage than me. She's fun to have around."
When asked whether the show had improved since the last time she was on the panel in 2008, Sharon joked, "Well, of course, because I'm back."
"I'm ecstatic to be reunited with my little Lou Lou," she added, referring to her sidekick judge Louis.
The first episode of this year's singing competition will kick off on Saturday 31 August, at 8pm.