Is authoritarian power ever legitimate? The contemporary political theory literature—which largely conceptualizes legitimacy in terms of democracy or basic rights—would seem to suggest not. I argue, however, that there exists another, overlooked aspect of legitimacy concerning a government’s ability to ensure safety and security. While, under normal conditions, maintaining democracy and rights is typically compatible with guaranteeing safety, in emergency situations, conflicts between these two aspects of legitimacy can and often do arise. A salient example of this is the COVID-19 pandemic, during which severe limitations on free movement and association have become legitimate techniques of government. Climate change poses an even graver threat to public safety. Consequently, I argue, legitimacy may require a similarly authoritarian approach. While unsettling, this suggests the political importance of climate action. For if we wish to avoid legitimating authoritarian power, we must act to prevent crises from arising that can only be resolved by such means.