AbstractThis article develops a theory of functional coexistence, a sustained negative peace which enables conflict parties and intermediaries to resist premature settlement and stay constructively engaged in an enduring state of nonresolution. The case studies of China‐Taiwan relations and the divided Europe and Germany during the Cold War illustrate essential qualities of functional coexistence. These qualities include the dynamic nature of the perceived boundaries of controlled interactions between adversaries who deny their opponents’ legitimacy and, in extreme cases, even their right to exist. Key lessons from the case studies are: (1) the need to build historical awareness of the shifting boundaries of mutually acceptable conflict behavior, (2) the imperative of finding a constructive way of staying engaged in intractable conflict, (3) the role of a multi‐layered, structural view of conflict intervention capable of resisting the inertia of hegemonic stability and submissive inaction, and (4) the importance of making use of short‐term actions to facilitate long‐term social change.