Past efforts to mitigate planet-level dangers have included modest initiatives such as climate treaties, arms control deals, or limited pandemic precautions, as well as bolder moves like the US government’s 1946 proposal for international control of atomic weapons, the 1972 Biological Weapons Convention, or Ronald Reagan’s 1983 missile shield initiative. While these were all important steps in the right direction, they have fallen far short of what is needed. In all cases, the most salient stumbling block has been the way every nation continues to fend for itself in a ruthlessly competitive world arena. An effective response to these four mega-dangers will require moving beyond the international self-help system and creating coordinated instruments of global governance.