John Joseph O'Neill (born 26 August 1957) is a musician who is the rhythm guitarist and principal songwriter of the punk rock/new wave band The Undertones. O'Neill, along with his younger brother Vincent and friends Feargal Sharkey, Michael Bradley and Billy Doherty, founded The Undertones in 1975, although Vincent O'Neill was replaced the following year with his younger brother Damian O'Neill, who became the band's lead guitarist. In 1985 the O'Neill brothers formed That Petrol Emotion, an acclaimed rock act who disbanded in 1994.