The relationship between populism and ethno-territorial politics has emerged repeatedly in empirical studies outside Western Europe. This article presents the main aim of the special issue, which is the systematically and empirically based investigation of the linkages between populism and ethno-territorial ideologies in Western European states. By introducing a conceptual map, in which the defining characteristics of populism, regionalism, state nationalism, and Euroscepticism are identified and conceptualized, the article proceeds with the possible linkage points between both concepts. It also proposes a smallest common denominator relationship between populism and ethno-territorial ideologies in that the notion of ‘homogeneous people’ becomes inexorably connected to the concept of ‘nation’ or ‘region’ pitted against political, economic, and cultural elites operating at various levels of government. By foreshadowing and discussing several of the key findings of the empirical case studies presented in this special issue, the introductory article highlights important emerging trends. Most crucially, only radical-right parties (both regionalist and state nationalist) appear to be inherently and stably populist. The same parties are also clearly Eurosceptic. By contrast, several regionalist parties, positioned in the mainstream left or right, tend to adopt a populist discourse only incidentally and temporarily.