This article examines Nietzsche’s moral psychology by focusing on his most important contribution to that form of inquiry, On the Genealogy of Morality. The will to power, understood as a self-standing desire for effective agency, emerges as a central concept. The Genealogy is an exploration of what happens to this desire under circumstances in which its satisfaction is severely restricted. In particular, phenomena playing a role in the development of morality such as ressentiment and self-denial are best understood as expressions of the “will to power of the weak.” And the moral outlook that grows out of them may be understood as a strategy to allow even the “weakest” a “feeling of power.” This moral outlook proves to be a kind of psychopathology insofar as it is an expression of the will to power that undermines the very conditions of its pursuit, satisfaction, and enjoyment—a “will to nothingness.”