Sogdiana (Sugdiane, O. Pers. Sughuda) was a province of the Achaemenian Empire, the eighteenth in the list in the Behistun Inscription of Darius the Great (i. 16), corresponding to the modern districts of Samarkand and Bokhara (in modern day Uzbekistan).

It lays north of Bactria between the Oxus (Amu Darya) and the Jaxartes (Syr Darya), and embraced the fertile valley of the Zarafshan (anc. Polytimetus).

Alexander the Great united Sogdiana with Bactria in to one satrapy. Subsequently it formed part of the Bactrian Greek kingdom, founded by Diodotus, until the Scythians occupied it in the middle of the third century BCE.

The Sogdians started to have contacts with China following the embassy of the Chinese explorer Zhang Qian. He wrote a report of his visit to Sogdian lands:

"Kangju (Sogdiana) is situated some 2,000 li (1,000 kilometers) northwest of Dayuan (in Ferghana). Its people are nomads and resemble the Yuezhi in their customs. They have 80,000 or 90,000 skilled archer fighters. The country is small, and borders Dayuan. It acknowledges sovereignty to the Yuezhi people in the South and the Xiongnu in the East." (Shiji, 123, Zhang Qian quote, trans. Burton Watson).

Following Zhang Qian' embassy and report, commercial Chinese relations with Central Asia and Sogdiana flourished, as many Chinese missions were sent throughout the 1st century BCE: "The largest of these embassies to foreing states numbered several hundred persons, while even the smaller parties included over 100 members... In the course of one year anywhere from five to six to over ten parties would be sent out." (Shiji, trans. Burton Watson).

Sogdians took an active part in the Silk Road trade, and were also actors in the Silk Road transmission of Buddhism, until the period of Muslim invasion in the 8th century.

The valley of the Zarafshan about Samarkand retained even in the Middle Ages the name of the Soghd O Samarkand. Arabic geographers reckon it as one of the four fairest districts in the world.

Today's Tajiks are the descendants of Sogdians and Bactrians.