The end of the First World War was a crucial time for nationalist leaders and minority communities across the European continent and beyond. The impact of the postwar spread of self-determination on the redrawing of Eastern European borders and on the claims of colonial independence movements has been extensively researched. By contrast, the international historiography has paid little attention to minority nationalist movements in Western Europe. This article focuses on three regions (Catalonia, Flanders and South Tyrol) that experienced considerable sub-state national mobilization in the interwar period. We aim to understand whether the leaders of Western European minorities and stateless nations shared the same enthusiasm as their anti-colonial and Eastern European counterparts for the new international order that selfdetermination seemed to foreshadow in the months following the end of the First World War. Because the American President Woodrow Wilson stood out as the most prominent purveyor of the new international legitimacy of self-determination, the article further examines how Western European nationalist movements exploited Wilson’s image and advocacy to achieve their own goals. Nationalist forces in Catalonia, Flanders and South Tyrol initially mobilized self-determination and referred to Wilson as a symbol of national liberation, but this instrumentalization of self-determination was not sustained. Large-scale mobilization occurred only in Catalonia, and, even there, it disappeared suddenly in spring 1919. Furthermore, sub-state nationalist movements in Western Europe tended to mobilize self-determination to gain regional autonomy, rather than full independence, thus pursuing internal, not external, self-determination. The willingness of these movements to privilege autonomy over full independence made them more receptive to compromise. Radical forces would become stronger only in the 1930s and largely for reasons not directly connected to the post-war mobilization around self-determination. ; Swiss ...