The Proto-Kartvelian language, or Common Kartvelian (Georgian: წინარექართველური ენა, ts'inarekartveluri ena), is the linguistic reconstruction of the common ancestor of the Kartvelian languages, which was spoken by the ancestors of the modern Kartvelian peoples. The existence of such a language is widely accepted by specialists in linguistics, who have reconstructed a broad outline of the language by comparing the existing Kartvelian languages against each other. Several linguists, namely, Gerhard Deeters and Georgy Klimov have also reconstructed a lower-level proto-language called Proto-Karto-Zan or Proto-Georgian-Zan, which is the ancestor of Karto-Zan (includes Georgian and Zan) languages.
The ablaut patterns of Proto-Kartvelian are highly similar to those of the Indo-European languages, and so it is widely thought that Proto-Kartvelian interacted with Indo-European at a relatively early date. This is reinforced by a fairly large number of words borrowed from Indo-European, such as the Proto-Kartvelian ṃḳerd (breast), and its possible relation to the Indo-European kerd (heart). Proto-Kartvelian *ṭep “warm” may also be directly derived from Indo-European *tep “warm”. It is also asserted that the name of wine in Indo-European languages is borrowed from Proto-Kartvelian *ɣwino, implicating quite close relations between these languages.
The modern descendants of Proto-Kartvelian are Georgian, Svan, Mingrelian and Laz. Of these, Mingrelian and Laz are often considered dialects of a single language, called Zan, although the two are not inherently mutually intelligible. The ablaut patterns of Proto-Kartvelian were better preserved in Georgian and (particularly) Svan than in either Mingrelian or Laz, in which new forms have been set up so that there is a single, stable vowel in each word element.
The system of pronouns of Proto-Kartvelian is distinct on account of its category of inclusive–exclusive (so, for instance, there were two forms of the pronoun "we": one that includes the listener and one that does not). This has survived in Svan but not in the other languages. Svan also includes a number of archaisms from the Proto-Kartvelian era, and therefore it is thought that Svan broke off from Proto-Kartvelian at a relatively early stage: the later Proto-Kartvelian stage (called Karto-Zan) split into Georgian and Zan (Mingrelo-Laz).