Tacheng (Qoqek/Sawesek) or Chöchek is a county-level city (1994 est. pop. 56,400) and the administrative seat of Tacheng Prefecture, in northern Ili Kazakh Autonomous Prefecture, Xinjiang, one of the autonomous regions of China.
The city was sometimes called Tarbaghatay or Tarbagatai (Mongolian: 'having marmots') and was once known in European languages as Chuguchak (based on its name in the Mongolian language). The current official Chinese name Tacheng is an abbreviation of "Tarbaghatay City". The current Uyghur name is Qöqäk Xäĥri.
It is located in the Dzungarian Basin, some 10 km (6.2 mi) from the Chinese border with Kazakhstan. For a long time it has been a major center for trade with Central Asia because it is an agricultural hub. Its industries include food processing, textiles, and utilities.
The city suffered harshly in 1865, during the fighting between the Qing forces and the Dungan and Uyghur rebels.
The Bakhtu border crossing into Kazakhstan is located 17 km (11 mi) from Tacheng. The checkpoint on the Kazakh side of the border is also known as Bakhty and is located 60 km (37 mi) from Makanchi in East Kazakhstan province. The border has been closed since 2009 for traffic both ways.
Tacheng has a typical Central Asian and Xinjiang cool semi-arid climate (Köppen BSk) that is almost moist enough to be a hot summer humid continental climate (Köppen Dfa), as being on the west side of the Altay Mountains the region receives more winter snowfall than most of Xinjiang.