This Handbook offers an introduction to the linguistically diverse languages of the Caucasus, spoken in southern Russia, Georgia, Azerbaijan, and Armenia. Three indigenous language families of the area include Nakh-Dagestanian, Northwest Caucasian (also known as Abkhaz-Adyghe), and South Caucasian (also known as Kartvelian). Languages of the Caucasus display a number of cross-linguistically unusual features rarely found elsewhere. The Handbook presents descriptions of language families of the area and individual languages within these families, with the linguistic profiles enriched by demographic and sociolinguistic research. In addition, the Handbook delves more deeply into theoretical analyses of linguistic features, such as sound systems, agreement, ellipsis, and discourse properties, which are found in some languages of the Caucasus.