The Qilian Mountains (Tsilien Mountains; Chinese: 祁连山; pinyin: Qílián 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.