The Tian Shan, also known as the Tengri Tagh or Tengir-Too, meaning the Mountains of Heaven or the Heavenly Mountain, is a large system of mountain ranges in Central Asia. The highest peak in the Tian Shan is Jengish Chokusu, at 7,439 metres (24,406 ft) high. Its lowest point is the Turpan Depression, which is 154 m (505 ft) below sea level.

One of the earliest historical references to these mountains may be related to the Xiongnu word Qilian (traditional Chinese: 祁連; simplified Chinese: 祁连; pinyin: Qílián) – according to Tang commentator Yan Shigu, Qilian is the Xiongnu word for sky or heaven. Sima Qian in the Records of the Grand Historian mentioned Qilian in relation to the homeland of the Yuezhi and the term is believed to refer to the Tian Shan rather than the Qilian Mountains 1,500 kilometres (930 mi) further east now known by this name. The Tannu-Ola mountains in Tuva has the same meaning in its name ("heaven/celestial mountains" or "god/spirit mountains"). The name in Chinese, Tian Shan, is most likely a direct translation of the traditional Kyrgyz name for the mountains, Teñir Too. The Tian Shan is sacred in Tengrism, and its second-highest peak is known as Khan Tengri which may be translated as "Lord of the Spirits". At the 2013 Conference on World Heritage, the eastern portion of Tian Shan in western China's Xinjiang Region was listed as a World Heritage Site. The western portion in Kazakhstan, Kyrgyzstan, and Uzbekistan was then listed in 2016.