The European Union treaty states that in its relations with the wider world, the EU is to promote peace, security, the protection of human rights, and the strict observance and the development of international law. The EU is active in peace processes around the world, yet its role in international peace mediation is largely ignored. This book offers the first scholarly analysis of how the EU engages in peace processes and justice for human rights violations, focussing on the point where mediation and transitional justice intersect. Drawing on extensive fieldwork, the book includes case studies of how the EU sought to promote peace and justice in the Democratic Republic of Congo (DRC), how it supports international justice through the International Criminal Court, and a model of the EU as a mediator. These provide an evidence-base for policy makers and practitioners as well as strong empirical contributions to theory. The book addresses whether and how the EU pursues its principles of both peace and justice in conflict zones, where, in practice, these principles may be in conflict, and the implications of these findings for understanding EU foreign policy and the EU as a security actor. This book will be of much interest to students of EU foreign policy, transitional justice, peace and conflict studies and security studies.