National Catholicism, which identifies the nation with the Catholic faith, submits Catholic universalism to the logic of an introverted nationalism that opposes sharing sovereignty with other nations both within the state and in the framework of supranational institutions like the European Union. The ascent of European accession and regional devolution to the top of the political agenda heightened the divisiveness of National Catholicism and made its legacy problematic in the aftermath of the democratic transitions (e.g. 1976 in Spain and 1989 in Poland). This book analyzes and describes the attempts to transform introverted conceptions of the nation into extroverted nationalism during the democratic transition and in the two decades thereafter.