Communal disputes over local issues such as land use, cattle herding, and access to scarce resources are a leading cause of conflict around the world. Over the coming decades, climate change, forced migration, and violent extremism will exacerbate such disputes in places that are ill equipped to handle them. UN peacekeeping operations are the international community’s primary tool for managing conflict. Despite abundant evidence that peacekeepers limit large-scale fighting between armed groups, we know little about their ability to prevent more localized forms of violence. Local Peace, International Builders explains the conditions under which UN peacekeeping operations promote peaceful interactions between civilian communities in fragile settings. Its central theoretical insight is that civilian perceptions of peacekeepers’ impartiality shape their ability to manage local disputes. To support this claim, I collected georeferenced data on the deployment of more than 100,000 peacekeepers to localities across Africa from 1999–2019. I also gathered data from extensive field research in Mali, a West African country with widespread violence managed by peacekeepers: nearly 50interviews with local political, religious, and traditional leaders, behavioral games with more than 500 Malians from 14 ethnicities, and surveys of 1,400 civilians. The book highlights a critical pathway through which UN peacekeeping may successfully maintain order in the international system. The findings have clear implications for how we think about international interventions—and how they can be better designed in the future to prevent violence in conflict and post-conflict settings.