Chagatai, also known as Turki, Eastern Turkic, or Chagatai Turkic, is an extinct Turkic language that was once widely spoken across Central Asia. It remained the shared literary language in the region until the early 20th century. It was used across a wide geographic area including western or Russian Turkestan, eastern or Chinese Turkestan, the Crimea, the Volga region, etc. Literary Chagatai is the predecessor of the modern Karluk branch of Turkic languages, which includes Uzbek and Uyghur. Turkmen, which is not within the Karluk branch but in the Oghuz branch of Turkic languages, was nonetheless heavily influenced by Chagatai for centuries.

The Turkic languages are a language family of more than 35 documented languages, spoken by the Turkic peoples of Eurasia from Eastern Europe and Southern Europe to Central Asia, East Asia, North Asia (Siberia), and West Asia. The Turkic languages originated in a region of East Asia spanning from Mongolia to Northwest China, where Proto-Turkic is thought to have been spoken, from where they expanded to Central Asia and farther west during the first millennium. They are characterized as a dialect continuum.