Kangju (; Eastern Han Chinese: khɑŋ-kɨɑ < *khâŋ-ka (c. 140 BCE)) was the Chinese name of a kingdom in Central Asia during the first half of the first millennium CE. The name Kangju is now generally regarded as a variant or mutated form of the name Sogdiana. According to contemporaneous Chinese sources, Kangju was the second most powerful state in Transoxiana, after the Yuezhi. Its people, known in Chinese as the Kāng (康), were evidently of Indo-European origins, spoke an Eastern Iranian language, and had a semi-nomadic way of life. They were probably identical to the "Saka" Sogdians, or other Iranian groups closely related to them, such as the Asii.
According to John E. Hill, a historian specialising in ancient Central Asia, "Kangju (W-G: K'ang-chü) 康居" was in or near the "Talas basin, [modern] Tashkent and Sogdiana". (According to Edwin Pulleyblank, Beitian – the summer capital of Kangju – was in or near modern metropolitan Tashkent.)
It is not clear whether the Chinese name 康居 Kangju was intended to transcribe an ethnic name, or to be descriptive, or both. 居 ju can mean: 'seat', 'central place of activity or authority; 'to settle down,' 'residence,' or 'to occupy (militarily).'... The term, therefore, could simply mean "the abode of the Kang," or "territory occupied by the Kang." ... As kang 康 means 'well-being', 'peaceful,' 'happy;' 'settle', 'stability,' Kangju can be translated as the 'Peaceful Land,' or 'Abode of the Peaceful (People).' ... Even if the name Kangju was originally an attempt to transcribe the sounds of a foreign name, it would still have carried the sense of a peaceful place to Chinese speakers, and the name 'Kang' would have had overtones of a peaceful people.
Later Chinese sources, during the Sui and Tang dynasties, refer to Kangju as the State of Kang (). By that time it was part of the Göktürk Khaganate.
Pulleyblank linked Kangju to the Tocharian A word kāṅka-, probably meaning "stone" and proposed that the Kangju were originally Tocharians who had migrated westward into Sogdia and established themselves in Chach (modern Tashkent).