The keyword anti-imperialism connotes a set of concepts about the violence of empire and the meaning of freedom. But the history of the usage of this keyword also informs us about the shape of history itself. “Anti-imperialism” came into wide circulation in the late nineteenth century across imperial metropoles and colonial peripheries. Anti-imperialism is not just a term for various concepts that are critical of empire, but also indexes a world-historical shift that occurred between 1898 and 1930, between the end of the Age of Empires (reaching its peak in the 1880s and 1890s with the European scrambles for colonial possessions and US American overseas expansion) and the dawn of the Age of Decolonization and Nation States (resulting in the Non-Aligned Movement of the 1950s and 1960s). We study here the bridge between the age in which discourses of imperialism were hegemonic and the age in which the discourse of postcolonial nation-states became normative.