Trationally, the term “enemy of all humanity” (hostis generis humani) referred to pirates. In contemporary international criminal law, it refers to perpetrators of crimes against humanity and other core. This essay traces the evolution of the concept, and then offers an analysis that ties it more closely to ancient tyrants than to pirates. Some object that the label is dehumanizing, and justifies arbitrary killing of the “enemy of humanity.” The essay admits the danger, but defends the concept if it is restricted to fair trials. Rather than dehumanizing its target, calling the hostis generis humani to account in a court of law is a way of recognizing that radical evil can be committed by humans no different from any of us.