Around the world, religion's influence on societies and politics is increasing. Arguably religion is today a more salient feature of international politics than at any point in the last 300 years. Yet this increase in religion's prominence comes at the precise time that religious expression has come under unprecedented assault from both state actions and communal hostilities involving religion. At the same time, religious extremism and violence have also been on the rise globally. This article makes the case that these two trends -repression of religion and resistance on the part of believers -are intertwined. Here, I survey four forms of violence: domestic religious terrorism, international religious terrorism, religious civil wars and interstate conflicts. In each case, I outline different pathways through which restrictions on religion lead to violence, marshal data derived and coded from conflict databases, and present brief case studies showing how states that hinder religious freedom are disproportionately more likely to both experience and give rise to all four forms of violence. On the other hand, religiously free countries are far less susceptible to and do not encourage religious violence. The article concludes with some recommendations for policy.