Social integration--a goal integral to the European project--has not followed economic integration. The main argument I set forth here is that European economic integration is producing the very opposite of its intended goals, namely, it is leading to cultural disintegration in the form of rising nationalism and radical right mobilization. Using cross-national statistical survey data, an original longitudinal dataset, in-depth interviews, and first hand observations, I examine various aspects of how nationalism manifests in contemporary Europe: as national identity, as support for radical right political parties, and as a process of political mobilization. I focus specifically on the cultural and political consequences of the EU integration process on the post-socialist countries of Eastern Europe. One consequence of European integration is Europeans' increasing tendency to identify more with their nations than with Europe. Analysis of Eurobarometer survey data from before and after the 2007-2009 economic crisis shows that Europeans' support for the European project is deeply tied to their identities: those who see themselves in primarily nationalist terms are more likely to oppose their country's continued membership in the EU as well as further European integration. the EU's response to the economic crisis drove European citizens to pull away from Europe: across all countries, Europeans saw themselves in increasingly nationalist, as opposed to European, terms. In countries that were hardest hit by the economic crisis, individuals turned towards their national governments and national identities in dramatically high numbers. European citizens have grown increasingly disillusioned with the EU, and this disillusionment, anchored by sense of detachment from the European project, has taken shape along nationalist lines. Over the last two decades, radical right parties that advocate for ethnic vision of national belonging have garnered increasing electoral support in both Western and Eastern Europe. Comparing electoral support for such parties across 27 European countries from 1991 to 2012 shows that, in contrast to conventional wisdom, economic decline does not explain differences in the electoral success of radical right parties in Western and Eastern Europe. Support for radical right parties is lower in the less prosperous Eastern than Western Europe, and differences in immigration rates cannot explain this divergence. Rather, I find that political stability and social trust are more important determinants of support for radical right parties. Whereas higher stability decreases support for radical right parties in all European countries, the effect is much greater in Eastern Europe. In other words, when the governing regime is perceived as unstable in an Eastern European country, a radical right party is more likely to win support than in a Western European country. The greater effect of political instability in Eastern European countries may explain why support for radical right parties begins to decline in those countries after the late 1990s just as the political and economic conditions were stabilizing after the post-socialist transition. As in the West, Eastern Europeans' have become more likely to see themselves in national, as opposed to European, terms and radical right parties have recently gained support in countries like Hungary and Ukraine. Yet, in terms of popular support for exclusionary ethic nationalism, it is the West that appears more backward. The fear for the "new Europe" is no longer about the integration of the East, but rather the disintegration of the West. Large comparisons, however, can only provide a snapshot of radical right mobilization. To answer why and how individuals join radical right movements, I trace the rise of a radical right movement in Ukraine by conducting over 100 in-depth interviews between 2009 and 2012 with members of Ukraine's radical right wing party, Freedom (Svoboda). I find that activists were primarily recruited to the movement through friendship networks, reflecting the recruitment practices of progressive social movements. A surprising finding of this case study is that even the most ardent radical right activists were ambivalent about the political aims or ideology of the party before joining. Rather, they developed well formed political beliefs after continued interaction with other activists and participation in political events. Individuals were thus radicalized through the process of mobilization. By showing that radical ideas result from the mobilization process, this finding builds on emerging research of right-wing activists challenging the underlying assumption of social movement theory that activists, and radical right activists in particular, join movements to express preexisting beliefs.