Languages from at least five genetically unrelated families are spoken in the Caucasus, but there are only three endemic linguistic families belonging to the region: Kartvelian, West Caucasian, and Northeast Caucasian. These families are rather heterogeneous in terms of the number of languages and the distribution of the speakers across them. The Caucasus represents a situation where languages with millions of speakers have coexisted with one-village languages for hundreds of years, and where multilingualism has always been the norm. The richness of Caucasian languages on every linguistic stratum is dazzling: here we find some of the largest consonant inventories, inflectional systems where the mere number of word forms strains credibility (one of the Caucasian languages, Archi, is claimed to have over a million and a half word forms), and challenging syntactic structures. The typological interest of the Caucasian languages and the challenges they present to linguistic theory lie in different areas. Thus, for Kartvelian languages, the number of factors at play in the verbal system make the task of the production of a correct verbal form far from trivial. West Caucasian languages represent an instance of polysynthetic polypersonal verb inflection, which is unusual not only for Caucasus but for Eurasia in general. East Caucasian languages have large systems of non-finite forms which, unusually, retain the ability to realize agreement in gender and number while their non-finite nature is determined by the inability to head an independent clause and to express certain morpho-syntactic categories such as illocutionary force and evidentiality. Finally, all Caucasian languages are ergative to some extent.