The Old Turkic script (also known as variously Göktürk script, Orkhon script, Orkhon-Yenisey script, Turkic runes) was the alphabet used by the Göktürks and other early Turkic khanates from 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 Nikolai 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 Khaganate. Additionally, a Yenisei variant is known from 9th-century Yenisei Kirghiz inscriptions, and it has likely cousins in the Talas Valley of Turkestan and the Old Hungarian alphabet of the 10th century. Words were usually written from right to left.
Many scientists, starting with Vilhelm Thomsen (1893), suggested that Orkhon script is derived from descendants of the Aramaic alphabet in particular via the Pahlavi and Sogdian alphabets of Persia, or possibly via Kharosthi used to write Sanskrit (cf. the Issyk inscription). Vilhelm Thomsen (1893) also mentioned some reports that the Orkhon script could derive from Hunno-Scythian alphabet, but rejected them as being specious. It has also been speculated that tamgas represent one of the sources of the Old Turkic script, but despite similarities in shape and forms, this hypothesis has been widely rejected as unverifiable, largely because early tamgas are too poorly attested and understood to be subject to a thorough comparison.
Contemporary Chinese sources conflict as to whether the Turks had a written language by the 6th century. The Book of Zhou, dating to the 7th century, mentions that the Turks had a written language similar to that of the Sogdians. Two other sources, the Book of Sui and the History of the Northern Dynasties, claim that the Turks did not have a written language. According to István Vásáry, Old Turkic script was invented under the rule of the first khagans and was modelled after the Sogdian fashion.