Introduction Since its inception, the Organization for Security and Co-operation in Europe (OSCE) has been promoting peace and security in regions where conflicts have occurred or where security has been under threat. It continues to develop strategies to achieve sustainable peace in its area, including in South-Eastern Europe—the focus of this reference guide. As a regional arrangement under Chapter VIII of the Charter of the United Nations, the OSCE is a key instrument for conflict prevention. Its work in this area includes the fostering of democratic governance and the rule of law, which aims to build resilience to emerging tensions and crises, and support sustainable political solutions to existing disputes and conflicts. Furthermore, the OSCE works toward building sustainable peace by contributing to post-conflict rehabilitation, including by supporting initiatives that foster reconciliation and dealing with the past. Activities in these areas are implemented by different members of the OSCE family but most importantly by the organization’s field operations. In addition to its field operations, the OSCE has a plethora of instruments at its disposal that support building peace and preventing conflict on a daily basis. These include, among others, thematic units within the OSCE Secretariat that address different phases of the conflict cycle—from early warning and early action, to crisis management and post-conflict resolution. Moreover, the OSCE’s three institutions—the High Commissioner on National Minorities, the Office for Democratic Institutions and Human Rights (ODIHR), 9