Cicero bequeathed to later political thought influential accounts of cosmopolitanism, empire, and just war theory. This chapter examines these themes in his De republica, De legibus, and De officiis. I argue that Cicero’s discussion evinces a nuanced and sensitive treatment of the universalism characteristic of the natural law cosmopolitan tradition and the particularism of the republican tradition. Cicero’s theorizing shows a greater coherence than most modern scholars suppose. Ultimately, his “patriotic cosmopolitanism” offers a rich response to a question of immediate importance in contemporary politics, where the place of the nation in our global order is hotly debated: how may our allegiances to our particular political communities square with our aspirations for global justice? For readers interested in “international relations,” Cicero remains good to think with.