Old Turkic (also East Old Turkic, Orkhon Turkic, Old Uyghur) is the earliest attested form of Turkic, found in Göktürk and Uyghur inscriptions dating from about the 7th century to the 13th century. It is the oldest attested member of the Orkhon branch of Turkic, which is extant in the modern Western Yugur language. Confusingly, it is not the ancestor of the language now called Uighur; the contemporaneous ancestor of Uighur to the west is called Middle Turkic.
Old Turkic is attested in a number of scripts, including the Orkhon-Yenisei runiform script, the Old Uyghur alphabet (a form of the Sogdian alphabet), the Brāhmī script, the Manichean alphabet, and the Perso-Arabic script.
Sources of Old Turkic are divided into three corpora:
In Unicode, the block Old Turkic is located from U+10C00 to U+10C4F. It is used to display the Old Turkic script.
The Old Turkic script (also known as variously Göktürk script, Orkhon script, Orkhon-Yenisey script) is the alphabet used by the Göktürk and other early Turkic Khanates during the 8th to 10th centuries to record the Old Turkic language.
The script is named after the Orkhon Valley in Mongolia where early 8th-century inscriptions were discovered in an 1889 expedition by Nikolay Yadrintsev. These Orkhon inscriptions were published by Vasily Radlov and deciphered by the Danish philologist Vilhelm Thomsen in 1893.
This writing system was later used within the Uyghur Empire. Additionally, a Yenisei variant is known from 9th-century Kyrgyz inscriptions, and it has likely cousins in the Talas Valley of Turkestan and the Old Hungarian script of the 10th century. Words were usually written from right to left.
Orkhon script is derived from variants of the Aramaic alphabet, in particular via the Pahlavi and Sogdian alphabets, as suggested by V. Thomsen, or possibly via Karosthi (cf., Issyk inscription).