The article analyzes a relatively unknown, yet influential, contemporary fundamentalist theology of revenge as put forward in the religious writings of Meir Kahane (1932–1990), the notorious militant nationalist. We seek to provide a theological context for this militancy, so as to display the motivational logic behind this troubling trend in Jewish thought and practice. While the doctrine itself has emerged only quite recently, it draws on theological ideas that reach back to the medieval period. In the article we outline the early sources and discussions (Biblical, Rabbinic, medieval, etc.) that constitute the background of Kahane’s radical theology of revenge.