The security of America’s space assets – and the sanctuary of space – is being challenged by increasingly credible threats that come from three primary sources. One threat is the potential weaponization of space, for which some advocate despite the realities of physics and strategy. Another threat comes from the rise of adversarial counterspace programs, which can destroy, disable, or disrupt U.S. space assets. The third threat results from the international system of governance which is in decline and unable to adequately preserve peace in space. In order to defeat these threats, the United States must exhibit leadership on the international stage, forging international rules that protect its interests. It must defend its space assets through enhanced and explicit deterrence measures. Finally, it must overhaul its fractured domestic institutions that manage space policy, space strategy, and the space budget. Only by addressing these issues can America rise to meet the space security challenges of tomorrow and continue to enjoy the economic and military benefits that it derives from space.