Catholicism's contribution to the development of nationalist ideology, and more generally to the process of European nation building in the nineteenth century, has been neglected. Most previous work has concentrated instead on varieties of liberal nationalism. In fact, Catholic intellectuals forged a whole nationalist discourse, but from traditional-conservative and orthodox doctrine. This essay charts a transnational path through Latin European countries, whose thinkers pioneered the theoretical development of Catholic nationalism. The Latin countries–France, Italy, and Spain, especially–were the homeland of Catholicism and theological, philosophical, historical, and political theories originating in it had a tremendous impact on the general formation of Western nationalism. This essay examines the formation, evolution, and consolidation of Catholic nationalism through “New Catholicism,” showing how the nation-state project and modernity itself were rethought in a new conservative and Catholic form.