Altishahr (Traditional Uyghur: آلتی شهر, Modern Uyghur: ئالتە شەھەر, Uyghur Cyrillic: Алтә-шәһәр; romanized: Altä-şähär or Alti-şähär), also known as Kashgaria, or Yettishar is a historical name for the Tarim Basin region used in the 18th and 19th centuries. The term means "Six Cities" in Turkic languages, referring to oasis towns along the rim of the Tarim, including Kashgar, in what is now southern Xinjiang Uyghur Autonomous Region of China.

The name Altishahr is derived from the Turkic word Alti ('Six') and Persian word shahr ('city'). The Altishahr term was used by Turkic-speaking inhabitants of the Tarim Basin in the 18th and 19th century, and adopted by some Western sources in the 19th century.

Other local words for the region included Dorben Shahr ('Four Cities') and Yeti Shahr ('Seven Cities'). Another Western term for the same region is Kashgaria. Qing sources refer to the region primarily as Nanlu, or the 'Southern Circuit'. Other Qing terms for the region include Huijiang (回疆, the 'Muslim Frontier'), Huibu (回部, the 'Muslim Region'), Bacheng (the 'Eight Cities'), or Nanjiang ('Southern Frontier').

In the 18th century, prior to the Qing conquest of Xinjiang in 1759, the oasis towns around the Tarim did not have a single political structure governing them, and Altishahr referred to the region in general rather than any cities in particular. Foreign visitors to the region would attempt to identify the cities, offering various lists.

According to Albert von Le Coq, the 'Six Cities' (Altishahr) referred to (1) Kashgar; (2) Maralbexi (Maralbashi, Bachu); (3) Aksu (Aqsu), alternatively Kargilik (Yecheng); (4) Yengisar (Yengi Hisar); (5) Yarkant (Yarkand, Shache); and (6) Khotan. W. Barthold later replaced Yengisar with Kucha (Kuqa). According to Aurel Stein, in the early 20th century, Qing administrators used the term to describe the oasis towns around Khotan, including Khotan itself, along with (2) Yurungqash, (3) Karakax (Qaraqash, Moyu), (4) Qira (Chira, Cele), (5) Keriya (Yutian), and a sixth undocumented place.

The term 'Seven Cities' may have been used after Yaqub Beg captured Turpan (Turfan), and referred to (1) Kashgar; (2) Yarkant; (3) Khotan; (4) Uqturpan (Uch Turfan); (5) Aksu; (6) Kucha; and (7) Turpan.

The term 'Eight Cities' (Uyghur Cyrillic: Шәкиз Шәһәр, Şäkiz Şähār) may have been a Turkic translation of the Qing Chinese term Nanlu Bajiang (literally 'Eight Cities of the Southern Circuit'), referring to (1) Kashgar, (2) Yengisar (3) Yarkant and (4) Khotan in the west and (5) Uqturpan, (6) Aksu, (7) Karasahr (Qarashahr, Yanqi), and (8) Turpan in the east.

Altishahr refers to the Tarim Basin of Southern Xinjiang, which was historically, geographically, and ethnically distinct from the Junggar Basin of Dzungaria. At the time of the Qing conquest in 1759, Dzungaria was inhabited by Oirats, steppe-dwelling, nomadic Mongols who practiced Tibetan Buddhism. In contrast, the Tarim Basin was inhabited by sedentary, oasis-dwelling, Turkic-speaking Muslim farmers, now known as the Uyghurs. The two regions were governed as separate circuits before the region became independent. Xinjiang was made into a single province in 1884.