The politics of legitimacy is central to international relations. When states perceive an international organization as legitimate, they defer to it, associate themselves with it, and invoke its symbols. Examining the United Nations Security Council, Ian Hurd demonstrates how legitimacy is created, used, and contested in international relations. The Council's authority depends on its legitimacy, and therefore its legitimation and delegitimation are of the highest importance to states. Through an examination of the politics of the Security Council, including the Iraq invasion and the negotiating history of the United Nations Charter, Hurd shows that when states use the Council's legitimacy for their own purposes, they reaffirm its stature and find themselves contributing to its authority. Case studies of the Libyan sanctions, peacekeeping efforts, and the symbolic politics of the Council demonstrate how the legitimacy of the Council shapes world politics and how legitimated authority can be transferred from states to international organizations. With authority shared between states and other institutions, the interstate system is not a realm of anarchy. Sovereignty is distributed among institutions that have power because they are perceived as legitimate. This book's innovative approach to international organizations and international relations theory lends new insight into relations between sovereign states and the United Nations, and between legitimacy and the exercise of power in international relations.