The politicisation of European governance has become an important subject in debates about the institutional design, day-to-day decision-making and democratic legitimacy of the European Union. This special issue takes stock of this development of politicisation research, including the theoretical development as well as the rapidly expanding body of empirical evidence. It synergises the various perspectives on politicisation of European governance, building on a common understanding of politicisation as a three-dimensional process involving increasing salience, polarisation of opinion and the expansion of actors and audiences involved in EU issues. The introduction outlines the central theoretical and conceptual questions concerning the politicisation of European governance and provides a guiding framework for the contributions to this special issue. The contributions document that a differentiated Europe leads to differentiated politicisation across times, countries and settings. The differentiated patterns, particularly across countries, present profound challenges to the future trajectory of European integration and its democratic legitimacy.