The American pop princess will be singing her hit Womanizer on the show – but only after all the contestants have sung a Britney classic in homage to the star.
Hannah Montana star Miley Cyrus will also be on the show, performing her new hit 7 Things.
Also for the first time this series, the public are deciding who will be sent home as there will no sing off and no judge vote.
Elsewhere, back in the finalist’s house, Eoghan and Diana have been pouring cold water on the idea the have a “blossoming romance”.
A statement released from the X Factor press office today says: “Very much just good friends and nothing more, the two youngest contestants in the house can’t quite understand why there is so much interest in them, but they continue to mess about together and fortunately it’s not damaged their friendship.”
Eoghan meanwhile is excited about singing the Britney hit Sometimes, and apparently he has a treat in store for the younger fans with his second song.
Spanish contestant Ruth Lorenzo however is attempting Britney’s Joan Jett cover hit I Love Rock and Roll and JLS are hoping to avoid being in the bottom two again.
Alexandra Burke will be singing Toxic backed by 14 dancers – including two rather buff men - which has delighted Alexandra no end as she’s recently split with her boyfriend.
Diana however will be singing I’m Not a Girl this Saturday, which she says is ironic as it feels very appropriate to her at the moment.
