The Western Regions or Xiyu is a historical name specified in the Chinese chronicles between the third century BCE to the eighth century CE that refers to the regions west of Yumen Pass, most often Central Asia or sometimes more specifically the easternmost portion of it (e.g.

Altishahr or the Tarim Basin in southern Xinjiang), though it is sometimes used more generally to refer to other regions to the west of China as well, such as the Indian subcontinent (as in the novel Journey to the West).Because of its strategic location astride the Silk Road, the Western Regions becomes historically significant since at least the third century BCE.

It is the site of the Han–Xiongnu War until CE 89.

In the sixth century, Emperor Taizong's campaign against Xiyu states leads to Chinese control of the region until the An Lushan Rebellion.The region becomes significant in later centuries as a cultural conduit between East Asia, the Indian subcontinent, the Muslim world and Europe, such as during the period of the Mongol Empire.

One of the most significant exports of the Western Regions is Buddhist texts, particularly the Mahāyāna sūtras, which are carried by traders and pilgrim monks to China.

The Tang dynasty monk Xuanzang crosses the region on his way to study in India, resulting in the influential Great Tang Records on the Western Regions upon his return to the Tang capital of Chang'an.