The past two decades have seen many social, political, and international relations (IR) theorists make extensive use of Michel Foucault’s theory of biopolitics—or how political power interacts with biological life. What has so far passed unnoticed, however, is that Foucault formulated his highly influential theory about how living populations became political objects in the context of an overarching concern with what he termed “the power to kill life itself.” This essay reassesses Foucault’s biopolitics in light of his broader discussion of the potentially existential threats posed by nuclear weapons and gene editing technology. In doing so, it invites readers to reassess Foucault’s famous critiques of both sovereignty and political universalism, while also providing a succinct introduction to his theories of power and the general history of anthropogenic existential threats. The article concludes by raising fundamental questions for political and IR theory concerning what happens when the biological survival of the human species ceases to be a necessary prerequisite for politics and instead becomes a contingent outcome of politics.