This book offers a general theory of violent radicalization and uses case studies from a variety of different countries and groups to illustrate this. The first and fundamental objective of the book is to provide an explanatory framework to understand phenomena related to violent radicalization, deradicalization, the prevention of radicalization and to political violence; in particular, that inspired by religion. The second objective follows from the first. Understanding violent radicalization of religious inspiration implies delving into two key concepts: violent radicalization and religion. This second objective is indeed elusive, since, on the one hand, many liberal democracies have undergone processes of secularization or, at least, have lost interest in examining religion in public debates. Therefore, rigorously exploring social problems where religion seems to be involved, in one way or another, is complicated. Moreover, the notion of violent radicalization, in turn, is highly contested and confused with other ideas, such as polarization, extremism, terrorism or nonviolent radicalization. Finally, the book aims to bring theory into dialogue with empirical phenomena, and to test it against concrete cases related to violent radicalization and its prevention, on the one hand, and religion, on the other. The book’s originality comes from both its innovative, methodological approach and its breadth, with cases from several countries (Spain, the United States, Ireland, India, Israel, Russia and Colombia) and different ideological groups (revolutionary communists, nationalist movements, Jihadist groups, white and black supremacists). This book will be of much interest to students of terrorism and political violence, radicalization, sociology and international relations in general.