This is a treatise on ontology – that is, the systematic study of being – that argues for the role of “vanishing” in the metaphysical structures of reality. The notion of vanishing might appear to have no more significance than as a descriptor of phenomenal, empirical, or perceptual reality. The thesis that vanishing has a place in ontology – one that is not grounded in the already formed structure of human experience, but is rather presupposed by it – therefore might not seem apropos. However, as we argue throughout this work, vanishing has indeed had more than an implicit role in the elaboration of many key philosophical and metaphysical problems. To make this case, this project offers a close study of two ontologies that we argue, in their own yet confluent ways, make vanishing operative as a metaphysical process: G. W. F. Hegel’s Science of Logic (1813/1832) and Gilles Deleuze’s Difference and Repetition (1968). Given what is predominately regarded as an antithetical relation between Hegel and Deleuze’s philosophical projects, this work traces the notion of vanishing between their arguments in order to complicate this established picture of their opposition. What we argue, in the final instance, is that in both cases vanishing involves a concern with developing an ontology of becoming in which the movement of disappearance is constitutive of reality as such. To make this case, we study four major notions of Hegel’s Logic where vanishing has a central role (being, finitude, infinite, and ground) and correlate Hegel’s insights with Deleuze’s account of “finite” and “infinite representation” in Difference and Repetition.