Critics of partition argue that it contributes to the perpetuation, rather than the amelioration, of territorial conflict. This paper engages with the theoretical debates on partition, focusing on the particular and illustrative case of Ireland. The island has been partitioned into two polities for a century. Opposition to the partition of Ireland has existed from the outset to the contemporary Brexit context. The argument is that while hostility to partition has experienced different forms –namely political and violent– and different degrees of intensity, there is a historical continuum of contestation against partition in Ireland. While the territorial issue was calmed by the 1998 Good Friday Agreement, Brexit has reanimated the border question, providing political momentum for those who aim to challenge the territorial status quo.