Comparative studies of imperial cosmopolitanism draw upon a conceptual history of a translated term. This chapter re-examines the conceptual history of cosmopolitanism upon which many sociopolitical histories rely. Through a new survey of the early Greek and Latin terms and passages conventionally associated with cosmopolitanism, it proposes that whereas the Stoic cosmopolitan (variously politēs tou kosmou, civis mundi, mundanus) was compatible with empire, Diogenes and Philo’s respective kosmopolitēs was not. Histories of “imperial cosmopolitanism” that take cultural pluralism—rather than egalitarian citizenship--as world-citizenship’s signifying element thus rely on one of two distinct traditions. The coda reiterates the need for greater awareness of vested histories of ancient and modern translation by briefly comparing first century BCE China’s Han Empire.