And Boyzone are in talks to perform for the first time since bandmate Stephen Gately's death.
The signings are a major coup for Simon Cowell, who has already signed up Lady GaGa, Rihanna and Shakira to appear.
And they should give the ITV1 series a major boost in its ratings war with BBC1's Strictly Come Dancing. A show source said: "We're going all out to annihilate Strictly this year. These big signings will really help us."
SuBo will sing her debut single Wild Horses, a cover of the Rolling Stones' hit, on Sunday November 22.
It'll be her first return to Fountain Studios in Wembley, North London, where she lost BGT to dance act Diversity.
Our source said: "Simon is very excited about Susan coming back but wants to make sure she excels.
"It's going to be nerve-racking for her being at the very same place where she lost Britain's Got Talent.
"The pressure can get to her and he's decided not to sign another big-name act for that night so everything is focused around her."
The X Factor finalists will perform their Michael Jackson charity single You Are Not Alone in the second performance slot instead.
Meanwhile the remaining members of Boyzone - Ronan Keating, Keith Duffy, Mikey Graham, and Shane Lynch - may appear on a results show next month.
Boyzone sang in last year's final after Stephen begged Louis to let them appear.
Our source said: "We're very hopeful of getting the boys but understand how sensitive the situation is.
"It's going to be a big deal for them performing for the first time since Stephen passed away - but he loved The X Factor so it would be a fitting tribute."
Tonight's star guests are Black Eyed peas and 2006 winner Leona Lewis, who told the News of the World: "I'm nervous.
"It's always nerve-wracking in front of Simon Cowell."
Shakira is the star guest next Sunday.
Rihanna and Alicia Keys are booked for November 29.
And Lady Gaga and George Michael will perform on seperate dates in December.
This article has 2 comments
Can anyone tell me the date of the X Factor Final and whether it will be in 2 parts? Will it be on 12th and 13th December do you think? I need to know!
By Sam. Posted November 8 2009 at 8:53 AM.
This will only really make sense to anyone who has read the Viz
Does anyone else think that Susan Boyle looks like Maw Bacon from the Viz?? least if they made a movie version of that she'd have a job in the bag!!
By Biffa Bacon. Posted November 8 2009 at 8:21 AM.