Scholars and policy makers debate whether elites and citizens hold different views of the legitimacy of international organizations (IOs). Until now, sparse data has limited our ability to establish such gaps and to formulate theories for explaining them. This article offers the first systematic comparative analysis of elite and citizen perceptions of the legitimacy of IOs. It examines legitimacy beliefs toward six key IOs, drawing on uniquely coordinated survey evidence from Brazil, Germany, the Philippines, Russia, and the United States. We find a notable elite-citizen gap for all six IOs, four of the five countries, and all of six different elite types. Developing an individual-level approach to legitimacy beliefs, we argue that this gap is driven by systematic differences between elites and citizens in characteristics that matter for attitudes toward IOs. Our findings suggest that deep-seated differences between elites and general publics may present major challenges for democratic and effective international cooperation.