The relationship between civil war and religion is a complex one. Civil wars are influenced in many different ways by religiously based factors. Different religiously based factors influence the onset, dynamics, and termination of civil wars. Religious factors have been examined both as causes of war and their dynamics and as factors behind how violence is prevented, conflict is managed, and peace is built. Whereas research on peace and conflict has often tended to neglect religiously focused explanations in favor of explanations based on strategic, economic, or other factors, research on religion and conflict has seen a resurgence in recent years. Research can be organized based on three different levels of analysis: (a) explanations relating to the religious group level, (b) explanations relating to the level of interrelationships between different religious groups, and (c) explanations relating to the level of the group’s relationship to the state. On the group level, religious beliefs, religious practices, religious constituency, and religious institutions play a role. On the intergroup level, two main debates center around the “clash of civilization” and religious demography. On the state-religion level, religious grievances and state favoritism can be seen as explanations for civil wars. As religiously defined conflicts are becoming more common, understanding more about the conditions under which religious factors influence civil wars’ onset, dynamics, and termination is vital.