Dating back to the very beginning of our knowledge of the events that constituted the Holocaust, some historians, social scientists, philosophers, theologians and public intellectuals argue that it was a unique historical, or even trans‐historical, event. The aim of this article is to clarify what the uniqueness question should be about and to ascertain whether there are good reasons for judging that the Holocaust is unique. It examines the core meanings of ‘unique’ that feature in the literature and identifies which of these is most apt for considering the possible uniqueness of the Holocaust. It then works out what it would take for the Holocaust to be unique in the appropriately rigorous sense, which is facilitated by inquiring into the nature of genocide. The key question turns on the relation of the Holocaust to genocide: was the Holocaust more than, or different from, genocide?