International organizations’ lives often extend far beyond the moment of their initial contracting. How IOs do adapt to shifting circumstances in their member states global geopolitical changes, and even internal dynamics within the IO itself? This special issue on the life cycle of international cooperation explores the ebbs and flows of the IOs that underpin the international system. Firm theory, organizational sociology, and agency theory all have incorporated life cycles perspectives into the study of organizations, but IR has yet to fully harness these frameworks. A life cycles approach centers on, first, incorporating the IO itself as the core unit of analysis and, second, the dynamic processes within IOs — including life stages such as false starts, consolidation, inertia, growth, revitalization, death, and succession. Incorporating these dynamic processes into our understanding of IOs reminds us that historically, IOs have always experienced periods of both flourishing and faltering. Grasping the mechanisms that drive these changes is indispensable for a thorough understanding of the international system’s vitality and resilience. Articles in this issue explore the durability of IOs in the face of crises; the measures that IOs deploy to legitimize their existence; the role of individual leaders’ rhetoric in IO vitality; the tradeoffs that member states face between pulling the plug on an IO versus creating a new institution; the effect of member-state IO withdrawal on the international system overall; and the mass public’s perceptions of such withdrawals.