Nationalism contributed to the disintegration of the Soviet Union and helped put an end to the epoch-defining East–West rivalry, while ethnic conflict rearranged borders and peoples across the post-communist regions. After these initial shocks, however, most international relations (IR) scholars saw a region that was generally on a path toward political stabilization and international integration. This belief was reflected in the predominance of research on democratization and civil society, privatization and economic transition, and integration with the European Union. Nearly two decades after the collapse of communism, a simmering ethnic conflict in Georgia has sparked another major geopolitical shift. Nationalism remains a potent force not only in the post-Soviet and post-communist regions, but also for IR more generally, in the “normal” politics of parties and elections, development and trade, foreign policy making, and even war making. Regarding the politics of eastern Europe and central Eurasia, at least three distinct international dimensions of post-communist nationalism can be identified: the immediate impact of national or ethnic conflict on state-to-state relations as well as conflict spillover; nationalism’s impact on the foreign policies of states, the ways in which domestic ethnic issues can shape foreign policy debates and decisions; and the transnational spread of nationalist ideology. Present circumstances offer an opportunity not only to end the animosity and even reverse the hardening of antagonistic post-Cold War identities, but also to assess the respective impact of cultural–historical, economic, and leadership factors on the ongoing development of national identity and nationalism.