The Battle of Qatwan (Chinese: ) was fought in September 1141 between the Qara Khitai (Western Liao dynasty) and the Seljuq Empire and its vassal-state the Kara-Khanid Khanate. The Seljuqs were decisively defeated, which signalled the beginning of the end of the Great Seljuk Empire.

Yelü Dashi (Chinese: 耶律大石; pinyin: Yēlǜ Dàshí; Wade–Giles: Yeh-Lü Ta-Shih; alternatively Chinese: 耶律達實; pinyin: Yēlǜ Dáshí), courtesy name Zhongde (重德), also known by his temple name Emperor Dezong of Western Liao (西遼德宗), was the founder of the Qara Khitai (Western Liao dynasty). He initially ruled as king from 1124 to 1132, then as emperor from 1132 to 1143. He was also known in Muslim sources as Nūshī Taifū, Qushqin Taifū or Qushqīn, son of Baighū. He fled the Liao dynasty in northern China as it was on the verge of destruction by the Jurchen-led Jin dynasty and moved westward into Central Asia where he established a new empire.