Open conflict between Barcelona and Madrid, the triumph of Corsican nationalists, a dynamic Scottish nationalism... The so-called regionalist parties are definitely on a roll throughout the old continent. This is both the consequence and the cause of a general crisis of territoriality that could herald the overcoming of the nation-state in the Europe that gave birth to it. This overcoming from below converges with the overcoming from above: European integration. Does this integration, which generates solidarity par excellence, lead these parties to work together, to ally themselves against their common enemy in order to shape a Europe in which their stateless nations would have their place? This research paper aims to answer this question.