The European Union has increasingly become an international and global actor in many if not most policy areas (including agriculture, communication, fisheries, health, human rights, environment, trade, etc.) – through transferral of related competence to the EU represented by the European Commission and/or through coordination of the foreign policies of EU member states. International institutions constitute particularly prominent fora for the EU’s pursuit of its international role. Treaty-based international regimes and formal international organizations have proliferated in recent decades, making them probably the most important fora for global governance. Based either on formal EC/EU membership or on coordination of the positions of individual EU member states, the EU has been one of the major players in multilateral institutions, thereby supporting multilateralism and international cooperation in general. This lecture series sets out to explore the notion of performance in international institutions, and then examines the performance of the EU in a range of international institutions.