While security has always been political, it has for the most part been considered a special kind of politics that closes down political activity and debate. This introduction reviews recent theoretical and empirical developments to argue that a research agenda that re-engages security through the prism of politicisation is better able to elucidate the growing range of actors, arenas and arguments visible in contemporary security governance. Based on recent literatures from Political Science and European Studies that – so far – have been largely ignored by Security Studies, it develops an analytical framework around three dimensions: controversy, mobilisation and arena-shifting. It showcases the relevance of this perspective through brief empirical illustrations on the post-Snowden controversy, public participation on security strategy-making, and the role of parliaments in security policy. The overall aim is to reopen conceptual questions on the relationship between security and politics, inspire innovative empirical work to study the diverse politics around security, and allow for more differentiated normative inquiries into the ambivalent consequences of politicisation.