Karasahr or Karashar (Uyghur: قاراشەھەر, romanized: Qarasheher), which was originally known in the Tocharian languages as Ārśi (or Arshi), Qarašähär, or Agni or the Chinese derivative Yanqi (Chinese: 焉耆; pinyin: Yānqí; Wade–Giles: Yen-ch'i), is an ancient town on the Silk Road and the capital of Yanqi Hui Autonomous County in the Bayingolin Mongol Autonomous Prefecture, Xinjiang.

The city, referred to in classical Chinese sources as Yanqi, was located on the branch of the Silk Route that ran along the northern edge of the Taklamakan Desert in the Tarim Basin.

The people and city were also known as Agni, although this may have been a later exonym, derived from the word for "fire" in an Indo-Iranian language such as Sanskrit (cognate to English "ignite").

The 7th century Buddhist monk Xuanzang transliterated Agni into Chinese as O-ki-ni 阿耆尼 (MC ZS: *ʔɑ-ɡiɪ-ɳˠiɪ standard: Āqíní).

In China, Han dynasty sources describe Yanqi (Ārśi / Agni) as a relatively large and important neighboring kingdom.

[4] From the 1st century BCE onwards, many populations in the Tarim Basin, including the Ārśi underwent conversion to Buddhism and, consequently, linguistic influence from Indo-Iranian languages, such as Pali, Sanskrit, Bactrian, Gandhari and Khotanese (Saka).

In the early 17th century, the Portuguese Jesuit lay brother Bento de Góis visited the Tarim Basin on his way from India to China (via Kabul and Kashgar).

De Góis and his traveling companions spent several months in the "Kingdom of Cialis", while crossing it with a caravan of Kashgarian merchants (ostensibly, tribute bearers) on their way to Ming China.