To what extent was the evolution of secularism in South and Southeast Asia between the end of the First World War and decolonisation after 1945 a result of transimperial and transnational patterns? To capture the diversity of twentieth-century secularisms, Clemens Six explores similarities resulting from translocal networks of ideas and practices since 1918. Six approaches these networks via a framework of global intellectual history, the history of transnational social networks, and the global history of non-state institutions. Empirically, he illustrates his argument with three case studies: the reception of Atatürk’s reforms across Asia and the Middle East; translocal women’s circles in the interwar period; and private US foundations after 1945.