Local autonomy has become an increasingly valued feature of local government in recent decades. Indeed, decentralization reforms implementing the provision of services closer to citizens have been a general trend. Nevertheless, there is little agreement on the definition of local autonomy and the way it can be operationalized and measured. The aim of this article is to draw upon decentralization and local government theories to propose a theoretically legitimized index of local autonomy that can be applied in a comparative perspective. The literature on the topic apprehends local autonomy either by sectorial approaches—legalistic, functional, organizational or political—or by combining similar dimensions in very different ways, without saying whether one is more important than the others. Having created and implemented a codebook of eleven indicators for thirty-nine European countries, the empirical findings, combined with theoretical considerations, lead us to suggest regrouping the indicators into seven constitutive dimensions of local autonomy. They highlight the fact that very different national local autonomy profiles exist among European countries. In addition, the local autonomy index, constructed by weighting the dimensions, shows significant disparities on either side of the continent.