Despite a rich theoretical literature on regional (in)stability, little is known about its empirical validity. This paper presents simulated experimental findings on spatial heterogeneity in regional (in)stability accross 264 regions belonging to 26 European countries. To do so, it develops a broad model of state fragmentation that reconciles the views of the dominant strands in the literature. In order to apply the model, a novel indicator of regional political distinctiveness is proposed, rooted in the discrepancy between regional and national electoral behavior. Calibrating our model to the current European situation, we find that Cataluña, Flanders and the Basque country are the regions currently most likely to break away. In line with these results, governments in all three regions have consistently vocalized demands for increased autonomy -or even secession -in recent years. Denmark, Hungary and Slovenia show up as the most secession-robust European countries.