This essay argues that Carl Schmitt’s postwar writings offer an original critique of biotechnology and utopian thinking. Examining the classics of utopian literature from Plato to Thomas More and Aldous Huxley, Schmitt illustrates the rise of utopianism that aims to transform human nature and even produce an artificial “human-machine.” Schmitt discovers a counterimage to the emerging era of biotechnology from a katechontic form of Christianity and maintains that human beings must recognize their shared humanity in God, warning us that without a realm of transcendence, the enemy no longer offers an existential mirror but begins to incarnate foreign values, which must be destroyed completely. By comparing Schmitt with Michel Foucault and Donna Haraway, it is also argued that Schmitt’s thinking unlocks a novel path to exploring the meaning and histories of biopolitics and posthumanism. From a Schmittian perspective, Foucault’s depiction of biopolitics appears as a mere prelude to the coming age of biotechnology that will lead us into a posthuman era. Demonstrating interesting contrasts with Haraway’s utopian vision of the cyborg, it is maintained that Schmitt’s thinking offers a distinctively conservative-Christian critique of posthumanism.