The theory and practice of international organizations is a dynamic and increasingly important dimension of international law and politics. This course provides an introduction to the field, focusing on the interaction between international law and politics in international organizations. It begins by briefly exploring theoretical perspectives on the role of international institutions and then provides an overview of the UN system as the main example of global and highly institutionalized organizations. The second part of the course addresses cross-cutting institutional issues, including law-making, judicial review, and the role of the executive head of an international organization. Particular attention will be given to issues of responsibility, legitimacy and accountability that are shaping most of the contemporary discourse on international organizations.