The consequences of the UK’s exit from the European Union have been much discussed, including the relationship between these developments and the UK’s territorial future. This article seeks to contribute to this debate, focusing on the Scottish and Welsh independence movements. It argues that the European Union has been key to the growing viability of these movements over recent decades, providing both an external means of validation to their overriding objective of independence, and a practical support mechanism for its pursuit outside of the context of national politics. Further, it argues that both movements have successfully exploited international institutions and networks to further their goals. Brexit, therefore, in depriving them of such avenues and halting their European institutionalisation presents a threat to their ongoing viability and harms the technical feasibility of Scottish and Welsh independence. These findings significantly disrupt the assumption that the rupture of Brexit makes Scottish (or indeed Welsh) independence more likely, let alone inevitable.