(Eastern) Saka or Sakan was a variety of Eastern Iranian languages, attested from the ancient Buddhist kingdoms of Khotan, Kashgar and Tumshuq in the Tarim Basin, in what is now southern Xinjiang, China. It is a Middle Iranian language. The two kingdoms differed in dialect, their speech known as Khotanese and Tumshuqese.
Documents on wood and paper were written in modified Brahmi script with the addition of extra characters over time and unusual conjuncts such as ys for z. The documents date from the fourth to the eleventh century. Tumshuqese was more archaic than Khotanese, but it is much less understood because it appears in fewer manuscripts compared to Khotanese. Both dialects share features with modern Pashto and Wakhi. The language was known as "Hvatanai" in contemporary documents. Many Prakrit terms were borrowed from Khotanese into the Tocharian languages.
The two known dialects of Saka are associated with a movement of the Scythians. No invasion of the region is recorded in Chinese records and one theory is that two tribes of the Saka, speaking the two dialects, settled in the region in about 200 BC before the Chinese accounts commence.
In the 11th century, it was remarked by Mahmud al-Kashgari that the people of Khotan still have their own language and script and did not know Turkic well. According to Kashgari some non-Turkic languages like the Kanchaki and Soghdian were still used in some areas. It is believed that the Saka language group was what Kanchaki belonged to. It is believed that the Tarim Basin became linguistically Turkified by the end of the 11th century.
Other than an inscription from Issyk kurgan that it is tentatively identified as Khotanese (although written in Kharosthi), all of the surviving documents originate from Khotan or Tumshuq. Khotanese is attested from over 2,300 texts preserved among the Dunhuang manuscripts, as opposed to just 15 texts in Tumshuqese. These were deciphered by Harold Walter Bailey. The earliest texts, from the fourth century, are mostly religious documents. There were several viharas in the Kingdom of Khotan and Buddhist translations are common at all periods of the documents. There are many reports to the royal court (called haṣḍa aurāsa) which are of historical importance, as well as private documents. An example of a document is .