This book develops and applies a novel kind of explanation: Empty-Base Explanation. While ordinary explanations have a tripartite structure involving an explanandum, a base of reasons why the explanandum obtains, and a link that connects the reasons to the explanandum, this book argues that there are explanations whose corresponding set of reasons is empty. This novel idea is located in the theoretical background of several fundamental philosophical issues. For example, it provides a convincing kind of ultimate or final explanation that completely and conclusively explains a phenomenon without involving other phenomena for which further explanations could be demanded. The possibility and fruitfulness of empty-base explanation is defended by general considerations from the theory of explanation, as well as concrete applications to the practice of explanation by status, the explanation of logical theorems, causal connections, and laws of nature, self-explanation, the use of IBE in metaphysics, the notion of zero-ground (which it provides with a solid theoretical footing), and ultimate explanation and its application to philosophical cosmology, the debate about the PSR, and the question of why there is anything at all. For this book, Yannic Kappes has received the 2022 De Gruyter Prize for Ontology and Metaphysics from the German Society for Analytic Philosophy (GAP).