This book is an introduction to the relationship between human language and ethnicity. Its purpose is to provide an overview of the main concepts, issues, and debates, as well as a guide to the key research findings in the field. It is the next volume in the Cambridge series “Key Topics in Sociolinguistics,” which is appropriate because language and ethnicity is perhaps the epitome of a key topic in our field. Many of the early sociolinguistic studies, which launched an entire research tradition, dealt with the relationship of language to ethnicity. Since then, numerous studies of individual communities in which ethnicity plays a role in language variation have been conducted. There is no single work, however, which provides an overview of the main issues and implications of these studies. There are several volumes with the terms “language” and “ethnicity” or “ethnic identity” in the title (e.g. Dow 1991, Fishman 2001), but these have tended to focus on questions of nationalism, language rights, and the role of language competence in group identity, rather than variation within a particular language. In other words, books that say they are about “language and ethnicity” are, in practice, more often about “bilingualism and nationality.” Because these macro-issues have been well covered in the literature, I have chosen not to address them in detail here, although where bilingualism or code-switching illuminates some interesting facet of identity construction, I have included it in the discussion.