Big Brother 2015, also known as Big Brother 16 and Big Brother: Timebomb, was the sixteenth series of the British reality television series Big Brother, hosted by Emma Willis and narrated by Marcus Bentley. The series launched on Channel 5 in the United Kingdom and TV3 in the Republic of Ireland on 12 May 2015 and ended on 16 July 2015, a week earlier than planned. This was the earliest launch of a Big Brother series since the show's inception in 2000. It is the fifth regular series and the thirteenth series of Big Brother overall to air on Channel 5, and is the first regular series to air in May since Big Brother 8 in 2007. It is also the first series to air in Ireland since its move to Channel 5 in 2011. On 2 February 2015, it was revealed that Willis had stepped down as a host on the show's spin-off series Big Brother's Bit on the Side, though Rylan Clark will continue.
The series launched under the new contract which renewed the show for a further three years. It is the first and only regular series to credit Denis O'Connor as creative director. On Day 17, Aaron Frew was ejected from the House after flashing fellow Housemate Joel Williams. It is the second series to feature returning housemates after Ultimate Big Brother with Nikki Grahame, Aisleyne Horgan Wallace, Brian Belo and Helen Wood taking part as long-term houseguests.