Many pressing environmental and security threats now facing the international community may be traced to the frontiers. From climate change and cyber-attacks to the associated challenges of space weaponization and orbital debris mitigation, solutions to all of these issues have at their root some form of regulation over the ‘global commons’. Yet governance over these spaces is now transitioning away from multilateral treaties to regional and bilateral accords. This book makes an original contribution by comparing and contrasting some of the principal issues facing the frontiers. It analyzes how and why existing governance structures are often failing to adequately meet global collective action problems, with special coverage on cybersecurity and Internet governance. It proposes a new way forward incorporating lessons from successful regimes as well as the interdisciplinary scholarship on polycentric governance, arguing that multi-stakeholder collaboration is imperative in order to avoid tragedies of the global commons.