Abstract: This article reviews recent research and evolving practice of community-based approaches to preventing and mitigating mass violence. It considers growing evidence that externally driven international interventions in response to violence are failing due to a lack of recognition and support for local actors, and increasing research into locally-led efforts, such as community protection strategies, early warning and response systems, interreligious peacebuilding, and post-atrocity trauma healing. Drawing from examples from a wide range of cases, including Rwanda, Burundi, Democratic Republic of Congo, Central African Republic, Colombia, and Sri Lanka, the article identifies key lessons for improving atrocity prevention policy and practice. Based on examination of the literature and case studies, it argues for a fundamental shift in the field of atrocity prevention from external interventionism toward supporting local peace agency.