This article examines the institutionalization of regions as spaces for politics by focusing on the Breton case. Here, regional actors have embarked upon new strategies of engagement within maritime policy and have claimed authority over this issue in the absence of any formal right to do so. This 'capturing' strategy involves two complementary processes: the social construction by actors of a territorial identity repertoire and the deployment of multi-positioning strategies. Through pursuing both simultaneously, political actors in Brittany have legitimized their access to a multitude of extra-regional decisional arenas and, consequently, have institutionalized Brittany as a space for maritime politics.