With a referendum set to take place on 23 June 2016 in a large and important European Union (EU) member state on whether it should remain within the Union or leave altogether, this year will prove crucial for all Europeanists. Brexit is a real possibility that both the Union and other member states must be prepared to plan for and eventually absorb the potential impact of. Whilst the process of ‘will they, won’t they’ will continue until the referendum, and even beyond, this level of uncertainty creates challenges for the existing actors with a stake in the process. This introductory contribution will set the scene for the ensuing debate, which flows from the various perspectives that each of the authors have with regard to the ultimate question of a Brexit. The three editors introduce the legal, political and economic themes that run through the articles, whilst simultaneously attempting to map out the trajectory for if, when and how a Brexit may actually occur, given the differing perspectives in the debate.