This thesis tries to expand the analysis of ethno-regional parties through an international comparative study of their electorates. Our focus is on international constants in sociological structure and ideological orientation. We explore the patterns and structures of four distinct ethno-regional parties' electorates covering almost the full spectrum of de Winter’s scale of ethno-regional party programmes: Plaid Cymru (PC) (Wales, United Kingdom), Scottish National Party (SNP) (Scotland, United Kingdom), Vlaams Blok/ Vlaams Belang (VB) (Flanders, Belgium), Christlich Soziale Union in Bayern (CSU) (Bavaria, Germany). Our analysis uses survey data of the 1990s and early 2000s through a series of specific multiple correspondence analyses and classifications. We focus on socio-demographical data in the first round of analysis and values and opinions in a second one. The results clearly show a close international comparability of ethno-regional party electorates and a number of voter types specific to this type of party. While their social structure is largely identical to other large parties their ideological structure is specific to them and shares strong similarities throughout the cases. We have been able to identify four distinct groups within each of the electorates (federalists, nationalists, protesters and contesters) that define an ethno-regional electorate. ; Cette thèse entreprend d'étendre l'analyse des partis ethno-régionalistes à travers une étude comparative de leur électorats. Nous portons une attention particulière aux déterminantes de structure sociale et démographique et les attitudes et opinions. Nous explorons les structures des électorats de quatre partis ethno-régionalistes qui couvrent presque l'intégralité de l'échelle de Winter des programmes politiques ethno-régionalistes: Plaid Cymru (PC) (Pays de Galles, Royaume-Uni), Scottish National Party (SNP) (Écosse, Royaume-Uni), Vlaams Blok/ Vlaams Belang (VB) (Flandre, Belgique), Christlich Soziale Union in Bayern (CSU) (Bavière, Allemagne). ...