Khitan or Kitan ( in large script or in small, Khitai;[2] Chinese: 契丹語, Qìdānyǔ), also known as Liao, is an extinct language once spoken in Northeast Asia by the Khitan people (4th to 13th century CE).

Owing to a narrow corpus of known words and a partially undeciphered script, the language has yet to be completely reconstructed.

[3] The History of Liao contains a volume of Khitan words transcribed in Chinese characters titled "Glossary of National Language" (國語解).

[7][8][9][10] The Qianlong Emperor of the Qing dynasty erroneously identified the Khitan people and their language with the Solons, leading him to use the Solon language to "correct" Chinese character transcriptions of Khitan names in the History of Liao in his Imperial Liao-Jin-Yuan Three Histories National Language Explanation (欽定遼金元三史國語解) project.

The Liao dynasty referred to the Khitan language with the term Guoyu (國語, "National language"), which was also used by other non-Han Chinese dynasties in China to refer to their languages like Manchu of the Qing, Classical Mongolian during the Yuan dynasty, Jurchen during the Jin, and Xianbei during the Northern Wei.