The Protectorate of the Western Regions (simplified Chinese: 西域都护府; traditional Chinese: 西域都護府; pinyin: Xīyù Dūhù Fǔ; Wade–Giles: Hsi1-yü4 Tu1-hu4 Fu3) was an imperial administration (a protectorate) situated in the Western Regions administered by Han dynasty China and its successors on and off from 59 or 60 BCE until the end of the Sixteen Kingdoms period in 439 AD. The "Western Regions" refers to areas west of Yumen Pass, especially the Tarim Basin in southern Xinjiang. These areas would later be termed Altishahr (southern Xinjiang, excluding Dzungaria) by Turkic-speaking peoples. The term "western regions" was also used by the Chinese more generally to refer to Central Asia.

The Tarim Basin is an endorheic basin in Xinjiang, Northwestern China occupying an area of about 888,000 km2 (343,000 sq mi) and one of the largest basins in Northwest China. Located in China's Xinjiang region, it is sometimes used synonymously to refer to the southern half of the province, that is, Southern Xinjiang or Nanjiang, as opposed to the northern half of the province known as Dzungaria or Beijiang. Its northern boundary is the Tian Shan mountain range and its southern boundary is the Kunlun Mountains on the edge of the Tibetan Plateau. The Taklamakan Desert dominates much of the basin. The historical Uyghur name for the Tarim Basin is Altishahr, which means 'six cities' in Uyghur. The region was also called Little Bukhara or Little Bukharia.