"Flatline" is a song by English girl group, "Mutya Keisha Siobhan", the original line up of the Sugababes. Written by the trio alongside British artist Dev Hynes, who also produced it, it was released via digital retailers on 6 September 2013 by Polydor Records, who signed the band in 2012. It is a pop and R&B song in which the drums and the male backing vocals get gradually stronger until a climactic part. Lyrically, it addresses the deterioration of a relationship. On 9 June 2022, the single and music video were re-released under the Sugababes name.