This chapter provides a sociolinguistic account of the languages of the Caucasus, including figures for speakers and their geographical distribution, language vitality, the official status of the languages, orthography, and writing practices. The chapter discusses language repertoires typical of different areas in the Caucasus, and their change over the 20th century. As a showcase, it provides an overview of traditional multilingualism in Daghestan, the most linguistically dense are in the Caucasus. It discusses various patterns of interethnic communication, including lingua franca and asymmetrical bilingualism. We show that bilingualism was gendered, and how Russian was spreading in the area as a new lingua franca. The chapter surveys the outcomes of language contact, covering both lexical borrowing (including main references to etymological research) and providing examples of structural convergence, with a special focus on the area of the highest language density in the Caucasus, Dagestan. Data in the chapter are based both on official sources (censuses), on information provided by experts and on the authors’ own work in the field.