Sogdiana ("Sug`ud","Sug`diyona" - Tajik, Sughd - Tajik, Sugdiane, Old Persian Sughuda, Persian:سغد, Chinese: Sute 粟特) was an ancient civilization of Persian peoples, then was a province of the Achaemenian Empire, the eighteenth in the list in the Behistun Inscription of Darius the Great (i. 16). Sogdiana, at different periods of time, included territories around Samarkand, Bukhara, Khujand and Kesh (Shahrisabz).

The Sogdian states, although never politically united, were centred around their main city of Samarkand. It lay north of Bactria, east of Khwarezm, and southeast of Kangju between the Oxus (Amu Darya) and the Jaxartes (Syr Darya), embracing the fertile valley of the Zarafshan (anc. Polytimetus). Sogdian territory corresponded to the modern districts of Samarkand and Bokhara currently Uzbekistan as well as modern Tajikistan. During the High Middle Ages it was extended to the north by a policy of colonial settlements up to the Lake Issyk Kul.

Sogdian Rock or Rock of Ariamazes, a fortress in Sogdiana, was captured in 327 BC by the forces of Alexander the Great, who 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 3rd century BC.

The Sogdians occupied a key position along the ancient Silk Road, and played a major role in facilitating trade between China and Central Asia. They started to have contacts with China following the embassy of the Chinese explorer Zhang Qian during the reign of Wudi in the former Han Dynasty, 141-87 BC. He wrote a report of his visit in Central Asia.

Following Zhang Qian's embassy and report, commercial Chinese relations with Central Asia and Sogdiana flourished, as many Chinese missions were sent throughout the 1st century BC: "The largest of these embassies to foreign 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). However the Sogdian traders were then still less important in the Silk Road trade than their Southern neighbours, Indian and Bactrian. They dominated the East-West trade after the 4th century AD up to the 8th century AD.

The Sogdians were noted for their tolerance of different religious beliefs. Buddhism, Manichaeism, Nestorian Christianity, and Zoroastrianism all had significant followings. Sogdians were actors in the Silk Road transmission of Buddhism, until the period of Muslim invasion in the 8th century. Much of our knowledge of the Sogdians and their language comes from the numerous religious texts that they have left behind.

The Sogdians spoke an East Iranian language called Sogdian -- closely related to Bactrian, another major language of the region in ancient times. Sogdian was written in a variety of scripts, all of them derived from the Aramaic alphabet.

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.

Minority of the Sogdian people gradually mixed with other local groups such as the Bactrians, Chorasmians & Greeks from Pamir.
Persians from Achaemenid empire spoken Persian (modern Tajiks).