‘Few political notions are at once so normative and so equivocal as internationalism’, wrote Perry Anderson 20 years ago. Little has changed: today too, internationalism tends to take the form of a regular exhortation to think or act beyond the border or boundary, yet its political content remains underdetermined. What do we mean when we talk about internationalism? The following discussion sought to approach this question not by returning to first principles – to a definition of internationalism that could stand outside of a given historical context – but by reconstructing different concepts of internationalism developed by a series of lesser studied political movements spanning the 20th century. Musab Younis discusses anticolonial and pan-African internationalisms of the 1920s–40s; Maria Chehonadskih interrogates the interwar Soviet internationalism of Alexander Boganov; Layli Uddin excavates the Islamic socialist activities of Maulana Bhashani; and Dilar Dirik focuses on the meanings of internationalism in the history of the Kurdistan Freedom Movement. These movements bore witness to a fundamental set of shifts in the nature of the international system as empires collapsed and new nation-states were born, while global structures of exploitation and extraction recomposed themselves in the Cold War and post-Cold War landscape. In this context, all conceived of internationalism as a fundamentally revolutionary project.