Brexit imposed a new binary on Northern Ireland politics which has interacted with the national question in complex ways. This interaction is the focus of this chapter. It begins by reviewing the position of the five main Northern Ireland parties on Europe prior to 2016. It explains the parties’ stances during the Brexit referendum campaign and examines how the parties responded to the referendum result. The chapter argues that Brexit produced constitutional restlessness in Northern Ireland because the vote lacked legitimacy according to the standards of consent contained in the 1998 Good Friday/Belfast Agreement. The chapter then traces how the new constitutional debate became established, highlighting how, although the debate was initiated by Brexit, it was intensified by subsequent developments in British and Irish politics. The chapter also explores key dilemmas that the debate posed for the political parties. The conclusion suggests that constitutional deliberations look set to continue but possibly at a lower intensity. Their direction will be shaped by developments in 2019-20 including the Boris Johnson Brexit agreement, the new Irish government, the restoration of devolution in Northern Ireland, and the coronavirus crisis.