Cheryl Cole - who was given her big break on TV talent show Popstars: The Rivals - will tell the X Factor hopefuls she can sympathise because she has been in their position.
The Girls Aloud star says: "I've been there and I have been here so I know how you are all feeling, I am just excited to see what you have got. [I] think it's going to be amazing and I wish you the best of luck from the bottom of my heart."
Other guest mentors include Tinie Tempah, who teams up with Tulisa Contostavlos, Ne-Yo who accompanies Nicole Scherzinger and Sharon Osbourne who is the sidekick to Louis Walsh.
Former X Factor judge Cheryl Cole will be back on the show tonight, almost two years after her departure.
Cole will return as a guest mentor, helping Gary Barlow put his acts from the older "overs" category through their paces during the judges' houses stage of the ITV1 talent show.
She bowed out from the UK X Factor after the 2010 series to take up a short-lived place on the panel for the US version of the show.