Over the last forty years, regions in Europe have acquired an increasingly important role in the provision of rights that were traditionally used by states to define the boundaries of national citizenship. Despite this trend, there are still few comparative examinations of what citizenship means for subnational actors, how these affect the provision of rights, and what the consequences of this process are for internal solidarity, the democratic process, and ultimately the constitutional integrity of modern states. These are important questions at a time when ideas about membership and rights within multilevel polities are vigorously contested in courts, legislative chambers, and election booths. Instances of these contestations are the Spanish Constitutional Court’s decision on the legality of subsequent referendums on Catalan secession in 2014 and 2017; the ongoing standoff between the state of California and the American federal government over who ought to regulate the rights of undocumented immigrants; and the Scottish and UK referendums on independence and exit from the European Union, respectively. This dissertation sets out to explain under what conditions, how, and with what kind of consequences some regions are more inclusionary than others in their approach to what citizenship entails and to whom it applies. This is what I refer to as the politics of regional citizenship. The empirical analysis focuses on subnational variations in the realisation of the right to health care for undocumented immigrants in three multilevel states where regional governments have some control over health care and, within these, on pairs of regions that have been governed by either left- or right-wing parties and coalitions: Lombardy (Italy, conservative government from 1995), Tuscany (Italy, progressive government from 1970), Andalusia (Spain, progressive government from 1980), Madrid (Spain conservative government from 1995), Vaud (Switzerland, progressive government from 2002) and Zürich (Switzerland, conservative government from 1991). Evidence is collected via the analysis of over 31 legislative documents and 62 interviews with policy-makers, health care professionals, and members of NGOs. The comparison shows that the interaction of political ideologies at different territorial levels leads to the emergence of contested ideas about citizenship through the use that regional governments make of the distinct traditions of regional protection of vulnerable individuals like minor children, the disabled, and the homeless. The comparison also shows that the structure of the territorial system of the state plays an important role in determining the direction of the politics of regional citizenship. The value assigned to territorial pluralism within a country, in particular, determines whether regional citizenship is developed against the state, as a strategy to manifest dissent and mark the difference—as is the case in Spain and, to some extent, in Italy—or, instead, together with the state, as an expression of multilevel differentiation—as in Switzerland. Importantly, however, regional citizenship does never develop in complete isolation from the state because it always represents an attempt to weaken or reinforce the policies of the central government.