The research unit "International Organizations" deals foremost with formal intergovernmental organizations such as the United Nations or the World Trade Organization, but also includes less formal and non-governmental international institutions in its studies. We treat international organizations (IOs) as part of a larger global governance system in which political authority is dispersed and contested among a wide range of state and non-state actors. IOs have not only grown in numbers but also gained in power since the end of the Cold War. In our research, we analyze consequences of both of these developments. First, we address the question of how collisions between institutions arising from their proliferation affect international cooperation and the international institutional order. Second, we focus on the role of IOs in addressing transboundary crises. As increasingly focal actors in times of regional or global distress, IOs encounter both windows of opportunity to wield authority and constraints imposed by member states and publics unwilling to cede sovereign control. Third, we study the current legitimacy crisis of the liberal international order. Here, we attempt to assess the extent to which characteristics of the order’s institutional setup, in particular its democratic deficits, might contribute to the popular backlash against multilateralism and IOs.