The dissertation analyzes the relationship between the securitization of immigration in the European Union (EU) and the increase of transnational movement within the continent, mainly since the 1990’s. The main purpose of the research is to examine how the EU has institutionalized the immigrant as an existential threat and how this process is related to the resistance of the nation-state as the locus of identity and condition to citizenship, even in the constitution of European citizenship. At the same time the EU has consolidated securitarian practices against the immigrant, reinforcing the exclusion already undertaken by its member states, it has suffered opposition from these same states, which, fearful of losing sovereignty, have also intensified the security measures on immigration. The study is based on Huysmans’ (2006) and Bigo’s (2002, 2007) framework on securitization and Balibar’s (2004a, 2004b, 2006) approach on transnational identity, as opposed to the idea of a postnational citizenship in Europe, sustained by authors like Habermas (1998, 2001, 2003). Besides an institutional emphasis, with the analysis of legislation and practices such as border controls and visa regulations, the research focuses on political discourses which identify the immigrant as a threat. Racism against Roma and muslims in the EU highlights how the status of nationality is not sufficient nowadays to not be considered an immigrant (Sayad, 1998, 2004), and how transnational mobility challenges the mythical purity of the modern nation-state’s identity.