This project examines disintegration referenda, that is referenda aimed at the partial or full withdrawal of individual member states from international institutions, which present a new but growing challenge to international cooperation. This project aims at improving our understanding how disintegration referendums challenge existing institutions and the remaining member states, and how they respond to such referendums. It focuses both on the actions of foreign governments during the referendum campaign and on how the negotiating processes and outcomes surrounding the negotiation process following a successful disintegration referendum affect regime stability by influencing domestic politics and public opinion in the remaining member states. Its theoretical contribution lies in conceptualizing disintegration referenda as a specific type of sovereignty referendum that confronts international institutions and their remaining members with a trade-off between economic prosperity and regime stability. Empirically, the project focuses on disintegration referenda in Greece, the UK, and Switzerland.