John Duncan, better known as Big John Duncan, is a Scottish musician who was the guitarist for the punk band The Exploited during their classic lineup from 1979 to 1984. He played and wrote the music for their albums Punks Not Dead, Troops Of Tomorrow and Let's Start a War. He also played and wrote many of their single releases, the most famous being "Dead Cities" which they performed on Top of the Pops in 1981.