In this article I locate some of the fundamental problems of self-determination within the context of an evolving international society. First, I argue that one particular manifestation of self-determination, that of national self-determination, is both a solution to the enduring problem of territorial legitimation in international relations as well as the source of subsequent challenges to territorial stability. Since the end of the Cold War, these challenges have been intimately linked with the growing number of civil wars as well as patterns of collective violence that blur the boundary between civil and inter-state war. Second, I claim that the dominant theoretical approaches to the study of world order in International Relations (IR) provide inadequate prescriptive guidance to cope with the challenges ahead. The article concludes by suggesting that, although secession may be justified under certain conditions in order to cope with the central paradox of national self-determination in international society, it is also an inadequate response. In the 21st century, the only enduring solution to the problems of self-determination is to sever the historical link between self-determination, nationalism and territorial sovereignty. In the final part of the article, I explore some of the ways in which it may be possible to transcend the tensions between territorial sovereignty and national self-determination in contemporary international relations.