The Oxford Handbook of Endangered Languages, in thirty-nine chapters, provides a comprehensive overview of the efforts that are being undertaken to deal with this crisis. Its purposes are (1) to provide a reasonably comprehensive reference volume, with the scope of the volume as a whole representing the breadth of the field; (2) to highlight both the range of thinking about language endangerment and the variety of responses to it; and (3) to broaden understanding of language endangerment, language documentation, and language revitalization, and, in so doing, to encourage and contribute to fresh thinking and new findings in support of endangered languages. The handbook is organized into five parts. Part I, Endangered Languages, addresses some of the fundamental issues that are essential to understanding the nature of the endangered languages crisis. Part II, Language Documentation provides an overview of the issues and activities of concern to linguists and others in their efforts to record and document endangered languages. Part III, Language Revitalization encompasses a diverse range of topics, including approaches, practices, and strategies for revitalizing endangered and sleeping (“dormant”) languages. Part IV, Endangered Languages and Biocultural Diversity, extends the discussion of language endangerment beyond its conventional boundaries to consider the interrelationship of language, culture, and environment. Part V, Looking to the Future, addresses a variety of topics that are certain to be of consequence in future efforts to document and revitalize endangered languages.