This special issue of International Affairs, launched on International Women’s Day 2016, explores the potential and limits of the Women, Peace and Security agenda, a global policy architecture supporting gender equality and today a significant reference point in the management and resolution of, as well as recovery from, violent conflict. The Women, Peace and Security (conventionally abbreviated to WPS) agenda was formally inaugurated by United Nations Security Council Resolution 1325 in October 2000. Across 18 operative paragraphs, the Council appealed for the greater participation of women in decision-making in national, regional and international institutions; their further involvement in peacekeeping, field operations, mission consultation and peace negotiations; increased funding and other support for UN bodies’ gender work; enhanced state commitments to women’s and girls’ human rights and their protection under international law; the introduction of special measures against sexual violence in armed conflict; and the consideration of women’s and girls’ needs in humanitarian, refugee, disarmament and post-conflict settings. It is our hope that this collection will forge a connection between the best of academic reflection on the agenda (via original research, political analysis and interrogating key terms and assumptions) and the concrete dilemmas of implementation (for participants, practitioners and activists). Fifteen years on from Resolution 1325, and after considerable progress in the recognition of gender issues, we offer our collective assessment of the vagaries of the Women, Peace and Security agenda, the better to understand the coming fortunes of the ‘the gender perspective’ on war and peace.