This article addresses the puzzle of why, and under what conditions, international organizations cease to exist. International relations literature offers rich explanations for the creation, design and effectiveness of international institutions and their organisational embodiments (international organizations, IOs), but surprisingly little effort has gone into studying the dynamics of IO termination. Yet if we want to understand the conditions under which IOs endure, we must also explain why they frequently fail to do so. The article formulates and tests a theory of 'IO death' using a combination of population-wide statistical analysis and detailed historical case studies. My analysis is based on an original dataset covering the period 1815-2016. I find that exogenous shocks are a leading proximate cause of IO terminations since 1815 and that organisations which are newly created and have small memberships and/or focus on issues with distributional consequences are more likely to succumb to environmental stress. My analysis leads me to suggest a number of extensions and refinements to existing institutionalist theories.