Actions to prepare for and prevent pandemics are a common topic for bioethical analysis. However, little attention has been paid to global catastrophic biological risks more broadly, including pandemics with artificial origins, the creation of agents for biological warfare, and harmful outcomes of human genome editing. What’s more, international policy discussions often focus on economic arguments for state action, ignoring a key potential set of reasons for states to mitigate global catastrophic biological risks: moral reasons. In this paper, I frame (...) the mitigation of such risks as a global public good, and I explore three possible categories of moral reasons that might motivate states to provide this global public good: nationalism, cosmopolitanism, and interstate obligations. Whilst there are strong objections to moral nationalism as a reason for states to act, moral cosmopolitanism may provide a broad reason which is further supplemented for individual states through the elaboration of interstate moral obligations. The obligations I consider are moral leadership, fairness, and reciprocity. Moral reasons for individual states action may more effectively or more appropriately motivate states to mitigate global catastrophic biological risks. (shrink)