Yelü in the context of "Kuchlug"

The Liao dynasty (/ljaʊ/; Khitan: Mos Jælud; traditional Chinese: 遼朝; simplified Chinese: 辽朝; pinyin: Liáo cháo), also known as the Khitan State (Mos diau-d kitai huldʒi gur), officially the Great Liao (Chinese: 大遼; pinyin: Dà Liáo), was a Khitan-led imperial dynasty of China and empire ruled by the Yelü clan that existed between 916 and 1125. Founded around the time of the collapse of the Tang dynasty, at its greatest extent it ruled over Northeast China, the Mongolian Plateau, the northern part of the Korean Peninsula, southern portions of Siberia, and the northern tip of the North China Plain.

The dynasty rose from the consolidation of power among the Khitans in the 8th century and their expansionist campaigns in the latter half of the 9th century. Eventually the Yila chieftain, Abaoji, became the leader of the Khitans and proclaimed a Chinese-style dynastic state in 916. The Liao dynasty launched multiple military campaigns against neighboring states and peoples including the Kumo Xi, Shiwei, Tatars, Zubu, Khongirad, Balhae, Goryeo, Later Tang, and the Song dynasty. Its conquests include the Sixteen Prefectures (including present-day Beijing and part of Hebei) by fueling a proxy war that led to the collapse of the Later Tang (923–936). In 1004, the Liao launched an expedition against the Northern Song dynasty. After heavy fighting and large casualties between the two empires, both sides worked out the Chanyuan Treaty. Through the treaty, the Liao forced the Northern Song to recognize them as peers and heralded an era of peace and stability between the two powers that lasted approximately 120 years. It was the first state to control all of Manchuria.

The Qara Khitai, or Kara Khitai (simplified Chinese: 哈剌契丹; traditional Chinese: 喀喇契丹; pinyin: Kālā Qìdān or Chinese: 黑契丹; pinyin: Hēi Qìdān; lit. 'Black Khitan'), also known as the Western Liao (Chinese: 西遼; pinyin: Xī Liáo), officially the Great Liao (Chinese: 大遼; pinyin: Dà Liáo), was a dynastic regime based in Central Asia ruled by the Yelü clan of the Khitan people. Being a rump state of the Khitan-led Liao dynasty, Western Liao was culturally Sinicized to a large extent, especially among the elites consisting of Liao refugees.

The dynasty was founded by Yelü Dashi (Emperor Dezong), who led the remnants of the Liao dynasty from Manchuria to Central Asia after fleeing from the Jurchen-led Jin dynasty conquest of northern China. The empire was usurped by the Naimans under Kuchlug in 1211; traditional Chinese, Persian, and Arab sources consider the usurpation to be the end of the dynasty, even though the empire would not fall until the Mongol conquest in 1218. Some remnants of the Qara Khitai would form the Qutlugh-Khanid dynasty in southern Iran.

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 as the Emperor Dezong of Western Liao (西遼德宗), was the founder of the Western Liao dynasty (Qara Khitai). He initially ruled as king from 1124 to 1132, then as emperor and gurkhan from 1132 to 1143. He was also known in Muslim sources as Nūshī Taifū, Qushqin Taifū or Qushqīn, son of Baighū. A member of the imperial Yelü clan, 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.

The Northern Liao (simplified Chinese: 北辽; traditional Chinese: 北遼; pinyin: Běi Liáo), officially the Great Liao (simplified Chinese: 大辽; traditional Chinese: 大遼; pinyin: Dà Liáo), was a dynastic regime of China, distinct from the Liao dynasty, established by the Khitan Yelü clan in northern China. The state only existed for a short period of time between 1122 and 1123.

Eastern Liao (simplified Chinese: 东辽; traditional Chinese: 東遼; pinyin: Dōng Liáo) was a 13th-century kingdom in what is now Northeast China, established by the Khitan Yelü clan in an attempt to resurrect the Liao dynasty. Its capital was situated in modern-day Kaiyuan, Liaoning.

Later Liao (simplified Chinese: 后辽; traditional Chinese: 後遼; pinyin: Hòu Liáo) was a short-lived dynastic regime in Northeast China that existed between 1216 and 1219. It was ruled by the House of Yelü and was the last regime that sought to revive the Liao dynasty in China (the Eastern Liao had by this time become a vassal of the Mongol Empire).