The X Factor is a British television music competition to find new singing talent. The fifth series was broadcast on ITV from 16 August 2008 until 13 December 2008. Dermot O'Leary returned to present the main show on ITV, while Fearne Cotton was replaced by Holly Willoughby as presenter of spin-off show The Xtra Factor on ITV2. Simon Cowell, Louis Walsh, and Dannii Minogue returned to the judging panel. Sharon Osbourne left after four series and was replaced by Cheryl Cole. The series was won by Alexandra Burke, with Cole emerging as the winning mentor. Auditions in front of producers were held in April and May, with callbacks in front of the judges in June. The number of applicants for series 5 reached an all-time high with a reported 182,000 people auditioning. A number of well-established music acts from around the world, such as Beyoncé, Mariah Carey, Britney Spears, Girls Aloud, Take That, Il Divo, and series 3 winner Leona Lewis, performed during the live stages of the show.

The X Factor is a British reality television music competition, created by Simon Cowell. Premiering on 4 September 2004, it was produced by Fremantle's British entertainment company, Thames, and Cowell's production company Syco Entertainment for ITV, as well as simulcast on Virgin Media One in Ireland. The programme ran for around 445 episodes across fifteen series, each one primarily broadcast late in the year, until its final episode in December 2018. The majority of episodes were presented by Dermot O'Leary, with some exceptions: the first three series were hosted by Kate Thornton; while Caroline Flack and Olly Murs hosted the show for the twelfth series.