Surveying civil war in the world today is striking in terms of how often religious cleavages and grievances have become central to armed conflict. How are the causes and outcomes of religious civil wars different than other civil wars, if at all? Is Islam implicated for the contemporary surge in religious civil war? The first section reviews the literature and addresses the importance of religion for civil war. I then introduce a dataset and describe key trends in religious civil war in the third section, while in the fourth section I present tests of whether Muslim or Arab Muslim societies in particular are more prone to religious strife. The paper concludes with a discussion of the implications of the main findings.