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.
More top news
Rain across central Britain with longer, intense downpours with thunder in places this evening. A lucky few will stay sunny and dry.
Planning on going to the London Marathon tomorrow? Read our handy guide first!
Labour plans to cap above-inflation rent rises over a three-year period, if they win the General Election.