Confounding the expectations of secularists, religion has a strong - perhaps growing - significance as a key source of identity for millions of people, especially in the developing world. In recent years, religion has made a muted but tangible impact in Western development circles, most commonly reflecting the view that religious hatreds and differences are central to many recent and current conflicts in the developing world. This paper argues that religion can both encourage conflict and build peace, reflecting growing evidence that religious forces can play a constructive role in helping to resolve conflicts. Religious individuals and faith-based organisations, as carriers of religious ideas, can play important roles, not only as a source of conflict but also as a tool for conflict resolution and peace-building, providing early warnings of conflict, good offices once conflict has erupted, and contributing to advocacy, mediation and reconciliation. Brief case studies of religious peacemakers - from Mozambique, Nigeria and Cambodia - demonstrate attempts, characteristically partially successful, to reconcile previously warring communities, thereby helping to achieve greater social cohesion, and providing a crucial foundation for progress in enhancing human development.