Proto-Turkic is the linguistic reconstruction of the common ancestor of the Turkic languages that was spoken by the Proto-Turks before their divergence into the various Turkic peoples. Proto-Turkic separated into Oghur (western) and Common Turkic (eastern) branches. Candidates for the proto-Turkic homeland range from western Central Asia to Manchuria, with most scholars agreeing that it lay in the eastern part of the Central Asian steppe, while one author has postulated that Proto-Turkic originated 2,500 years ago in East Asia.

The oldest records of a Turkic language, the Old Turkic Orkhon inscriptions of the 7th century Göktürk khaganate, already shows characteristics of Eastern Common Turkic. For a long time, the reconstruction of Proto-Turkic relied on comparisons of Old Turkic with early sources of the Western Common Turkic branches, such as Oghuz and Kypchak, as well as the Western Oghur proper (Bulgar, Chuvash, Khazar). Because early attestation of these non-easternmost languages is much more sparse, reconstruction of Proto-Turkic still rests fundamentally on the easternmost Old Turkic of the Göktürks, however it now also includes a more comprehensive analysis of all written and spoken forms of the language.

The Proto-Turkic language shows evidence of influence from several neighboring language groups, including Eastern Iranian, Tocharian, and Old Chinese.