Lostprophets /lɒstˈprɒfɪts/ were a Welsh rock band from Pontypridd formed in 1997. Founded by lead vocalist and lyricist Ian Watkins, bassist (later guitarist) Mike Lewis, drummer Mike Chiplin and guitarist Lee Gaze, they were originally a side-project to hardcore punk band Public Disturbance. They were also part of the Cardiff music scene.

Lostprophets released five studio albums, with their final release Weapons released on 2 April 2012. The band achieved two Top 10 hits on the UK Singles Chart ("Last Train Home" and "Rooftops"), one number-one single on the US Alternative Songs chart ("Last Train Home"), several Kerrang! Awards and nominations, and sold 3.5 million albums worldwide.

In December 2012, Watkins was charged with multiple sexual offences against children. The band cancelled all tour dates, and the other members announced the disbanding of Lostprophets in October 2013 before the end of Watkins' trial. Watkins pleaded guilty to several (but not all) charges in November 2013, and in December 2013 was sentenced to 29 years imprisonment plus six years on licence. In June 2014, the remaining members formed No Devotion with American singer Geoff Rickly as their lead vocalist.