The UNESCO atlas on endangered languages recognizes the Ryukyuan languages as constituting languages in their own right. This represents a dramatic shift in the ontology of Japan’s linguistic make-up. Ryukyuan linguistics needs to be established as an independent field of study with its own research agenda and objects. This handbook delineates that the UNESCO classification is now well established and adequate. Linguists working on the Ryukyuan languages are well advised to refute the ontological status of the Ryukyuan languages as dialects. The Ryukyuan languages constitute a branch of the Japonic language family, which consists of five unroofed Abstand (language by distance) languages.The Handbook of Ryukyuan Languages provides for the most appropriate and up-to-date answers pertaining to Ryukyuan language structures and use, and the ways in which these languages relate to Ryukyuan society and history. It comprises 33 chapters, written by the leading experts of Ryukyuan languages. Each chapter delineates the boundaries and the research history of the field it addresses, comprises the most important and representative information.