The twelfth UK series of The X Factor began on ITV on 29 August 2015. The live shows started on 31 October. In a change from previous series, there were seven weeks of live shows instead of the usual ten. Viewers were asked to decide which categories would be assigned to each judge by voting on Twitter during the series premiere. The results were announced on the day the Six Chair Challenge was filmed. Nick Grimshaw mentored the Boys, Rita Ora mentored the Girls, Simon Cowell mentored the Overs and Cheryl Fernandez-Versini mentored the Groups.

The twelve chosen finalists were Ché Chesterman, Seann Miley Moore, Mason Noise, Louisa Johnson, Lauren Murray, Kiera Weathers, Bupsi, Anton Stephans, Max Stone, Alien Uncovered, 4th Impact and Reggie n Bollie. On 29 October, Monica Michael (from the Girls category) was announced as the only wildcard on this series, with all four judges agreeing on it.