Over the past two decades, potential adversaries have developed a wide array of means to disrupt or deny the United States and its allies access to space capabilities that are essential to their security and military operations. This situation and deepening great-power tensions have given new urgency to understanding the counterspace strategies of potential adversaries and how they can be deterred from attacking U.S. and allied space assets or be dissuaded from even developing certain counterspace capabilities. There is no broadly agreed-on framework on the nature and requirements of deterrence in space operations. This report presents such a framework. The authors begin by identifying several foundational principles of deterrence and then consider what lessons pursuit of deterrence in other domains—nuclear and cyber—have for deterrence in space. They examine the nature and requirements of deterrence in the space domain, what constitutes success in space deterrence, what thresholds might lead to a failure of deterrence, and selected national approaches to space deterrence—by China, Russia, France, Japan, and India. Integrating all these components, the authors present three archetypes for space deterrence and consider questions about their application. They conclude that a comprehensive approach to space deterrence is likely to be most successful and should be tailored to address the distinct risk calculus and informational needs of various adversaries across the phases of conflict. Strategic messaging, selective revelation of space capabilities, and development of norms of responsible space behavior can also help deter attacks on space systems.