Coordinates: The Cilien Mountains (Chilien Mountains; Chinese: 祁連山山; pinyin: Cílien Shān; Wade–Giles: Ch'i2-lien2 Shan1; Mongghul: Chileb), also known as Nan Shan (Chinese: 南山, literally "Southern Mountains", as it is to the south of Hexi Corridor), is a northern outlier of the Kunlun Mountains, forming the border between Qinghai and the Gansu provinces of northern China.
The eponymous Qilian Shan peak, situated some 60 km south of Jiuquan, at , rises to 5,547 m. It is the highest peak of the main range, but there are two higher peaks further south, Kangze'gyai at with 5,808 m and Qaidam Shan peak at with 5,759 m.
The range continues to the west as Yema Shan (5,250 m) and Altun Shan (5,798 m). To the east, it passes north of Qinghai Lake, terminating as Daban Shan and Xinglong Shan near Lanzhou, with Maoma Shan peak (4,070 m) an eastern outlier. Sections of the Ming Dynasty's Great Wall pass along its northern slopes, and south of northern outlier Longshou Shan (3,616 m).
The Qilian mountains are the source of numerous, mostly small, rivers and creeks that flow northeast, enabling irrigated agriculture in the Gansu Corridor (Hexi Corridor) communities, and eventually disappearing in the Alashan Desert. The best known of these streams is the Ejin (Heihe) River.
The Shiji mentions the "Qilian mountains" together with Dunhuang as the homeland of the Yuezhi. A scholar however has suggested that the name here refers to the mountains now known as Tian Shan, 1,500 km to the west, and Dunhuang may be the Dunhong mountain. Qilian (祁连) is said to be as a Xiongnu word meaning "sky" (Chinese: 天) by Yan Shigu, a Tang Dynasty commentator on the Shiji.
The mountain range gives its name to Qinghai's Qilian County.
- Association for Asian Studies, Far Eastern Association (U.S.) (2003). The Journal of Asian studies, Volume 62, Issue 1. Association for Asian Studies. p. 262. ISBN 0-691-09676-7. Retrieved 2010-06-28.
- "Qilian Mountains conifer forests". Terrestrial Ecoregions. World Wildlife Fund.
- Liu, Xinru, Migration and Settlement of the Yuezhi-Kushan: Interaction and Interdependence of Nomadic and Sedentary Societies (2001) 
- Winchester, Simon. (2008). The Man Who Loved China: the Fantastic Story of the Eccentric Scientist Who Unlocked the Mysteries of the Middle Kingdom, p. 126.
- Winchester, Simon. (2008). The Man Who Loved China: the Fantastic Story of the Eccentric Scientist Who Unlocked the Mysteries of the Middle Kingdom. New York: Harper. ISBN 978-0-06-088459-8
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