More than ever, international security and economic prosperity depend upon safe access to the shared domains that make up the global commons: international waters, international airspace, outer space, and cyberspace. Together these domains serve as essential conduits through which the international system comprised of commerce, communication, and governance prospers. It is long-standing U.S. policy to maintain free and safe access to the commons for all who would use it for peaceful purposes. But the global commons are congested, contested, and competitive. The aim of this volume is to identify threats to safe access to the commons and to recommend strategies and partnerships for responsible and sustainable use of the commons. This volume provides a comprehensive approach that will enhance, influence, and align commercial industry, civil agency, and military branch perspectives on this complex topic.