How visible is international politics among mass publics? What accounts for variability in citizen knowledge of international politics? This study examines several conventional theories of political knowledge in the context of the United Nations (UN). Multi-level analysis of survey data from 17 Asian and European countries yields three main results. First, identification with a global community provides a powerful impetus for individuals to gather and retain information about UN politics. Second, wealthier citizens know more about UN politics, especially if they live in countries with greater economic inequality. Third, domestic political institutions shape citizen knowledge about UN politics, in particular the electoral system, legislative-executive relations, and federalism. The results of this study help clarify the sources of public knowledge of UN politics, understand differences in citizens’ ability to react critically to international politics, and underline the necessity for future research about mass publics’ knowledge about international politics.