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.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 Mongolian language).