In recent years, there has been a growing interest in the international dimensions of populism, by now a major political phenomenon around the world. This interest, however, has been confined largely to the state level, especially the influence of populism on foreign policy. In this Forum, we argue that it is important for analysis to move beyond the state level and view populism as a concept and phenomenon of international relations (IR) rather than simply a factor of foreign policy. The Forum discusses implications of the rise of populism for IR theory, the role of international systemic change in the emergence of populism in national arenas, and the ways that regime type, state structure and institutions, ideational content, and the political strategies of populists condition the impact of populism on world politics. In this way, the Forum identifies specific directions for the study of populism in IR that scholars can follow in the future.