Chagatai (جغتای Jağatāy) is an extinct Turkic language which was once widely spoken in Central Asia, and remained the shared literary language there until the early 20th century. It was also spoken by the early Mughal rulers in the Indian subcontinent, where it influenced the development of Hindustani. Ali-Shir Nava'i was the greatest representative of Chagatai literature.

As part of the preparation for the 1924 establishment of the Soviet Republic of Uzbekistan, Chagatai was officially renamed "Old Uzbek", which Edward A. Allworth argued "badly distorted the literary history of the region" and was used to give authors such as the 15th-century author Ali-Shir Nava'i an Uzbek identity.

Early development of the language is sometime known as Middle Turkic, or even simply Turki.

Etymology

The word Chagatai relates to the Chagatai Khanate (1225 –1680s), a descendant empire of the Mongol Empire left to Genghis Khan's second son, Chagatai Khan. Many of the Chagatai Turks and Tatars, who were the speakers of this language, claimed descent from Chagatai Khan.