Politicisation, in a broad and basic understanding, means to turn something – an issue, an institution, a policy – that previously was not a subject to political action into something that now is subject to political action. So far, most definitions of the concept would agree. But besides this basic approach, there is much discussion: Politicisation is a concept that is currently much used in the social sciences, and also a concept that is contested in its definitions and understandings. Several paths and subdisciplines contribute to the debate, but they are not necessarily connected to one another. Political theory or political economy discusses politicisation and also what can be termed the counter-concept, depoliticisation, theoretically and often with a normative background, whereas comparative politics and EU studies have increasingly taken to deliver empirical studies on the politicisation of the European Union. These latter studies most often rely on the indicators of salience, actor involvement and polarisation in and of political debates and processes. International Relations, last not least, increasingly discusses the politicisation of international politics and international organisations.