The thesis focuses on Regionalisms and Nationalisms in Europe with particular reference to the Catalan and Scottish cases. Following an historical and juridical approach the author debates on nationalism movements in Catalonia and Scotland through a comparative analysis of these two different nationalisms and it dedicates part of the research to the study of the European Union policies and orientation in promoting regional participation and devolution processes. In the thesis is stressed the existing link between regional/national movements and the European Union integration process and it is developed the discussion about the European Union's regulation for regions, regional communities and sub-state actors. Lastly the author traces the possible scenarios in Europe after the referendum in Scotland in 2014 and the reflections in Catalonia as well.