Known primarily for his work on technology and Christian anarchism, Ellul is nevertheless an important figure within radical theology as well. Along with his good friend, Gabriel Vahanian, Ellul is one of radical theology's most sociologically oriented thinkers. This chapter begins by covering the ways in which Ellul was influenced by Barth, Kierkegaard, and Marx. It then describes Ellul's sociological and theological works in depth. The chapter concludes by discussing Ellul's relationships with other radical theologians, Harvey Cox and William Hamilton.