Kangju 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. The Sogdians may have been the same people as those of Kangju and closely related the Sakas, or other Iranian groups such as the Asii.

Sogdia or Sogdiana was an ancient Iranian civilization between the Amu Darya and the Syr Darya, and in present-day Uzbekistan, Turkmenistan, Tajikistan, Kazakhstan, and Kyrgyzstan. Sogdiana was also a province of the Achaemenid Empire, and listed on the Behistun Inscription of Darius the Great. Sogdiana was first conquered by Cyrus the Great, the founder of the Achaemenid Empire, and then was annexed by the Macedonian ruler Alexander the Great in 328 BC. It would continue to change hands under the Seleucid Empire, the Greco-Bactrian Kingdom, the Kushan Empire, the Sasanian Empire, the Hephthalite Empire, the Western Turkic Khaganate and the Muslim conquest of Transoxiana.