Chaghaniyan (Middle Persian: Chagīnīgān; Persian: چغانیان Chaghāniyān), known as al-Saghaniyan in Arabic sources, was a medieval region and principality located on the right bank of the Oxus River, to the south of Samarkand.

Chaganian was an "Hephthalite buffer principality" located between Denov and Termez, and became a sanctuary for the Hephthalites following their defeat against the Sasanian Empire and the First Turkic Khaganate in 563-567 CE. They resettled in Chaganian and other territories of Tokharistan, under their new king Faghanish, who established a dynasty. Soon, the new Hephthalite territories north of the Oxus, to which Chaganian belonged, fell under Western Turk suzerainty, while the territories south of the Oxus were nominally controlled by the Sasanian Empire. The territories under the Turks rebelled in 581 CE.

Their coinage in Chaganian was an imitation of the Sasanian coins of Khusrau I, with sometimes the addition of the name of local rulers.

In 648-651 CE an ambassador from Chaganian named Pukarzate is known to have visited king Varkhuman of Samarkand, and appears in the Afrasiyab murals, together with other Central Asian ambassadors. An adjoining inscription reads: "I am Pukarzate, the dapirpat (chancellor) of Chaganian. I arrived here from Turantash, the lord of Chaganian". The King of Chaganian named Turantash may have a been a "Hunnic" Hephthalite ruler, or one of the local Chaghan Khudah, who seem to have coexisted with the Hephthalites.

During its early history, the region often shifted between Sasanian and Hephthalite control. By the late 7th-century, Chaghaniyan came under the control of presumably Iranian local rulers known as the “Chaghan Khudah”. During the Muslim conquest of Persia, the Chaghan Khudah aided the Sasanians against the Rashidun Arabs. However, the Arabs, after having dealt with the Sasanian Empire, began focusing on the local rulers of Khorasan, which included the Chaghan Khudah and many other local rulers. In 652, the Chaghan Khudah, along with the rulers of Talaqan, Guzgan, and Faryab, aided the ruler of southern Tokharistan, the Western Turk Yabghus of Tokharistan, against the Arabs. Nevertheless, the Arabs managed to emerge victorious. However, the Rashidun Caliphate soon fell into civil war, and was conquered by another Arab family, who founded the Umayyad Caliphate in 661.

Under the leadership of Ziyad ibn Abihi, the Umayyad viceroy of the eastern Caliphate, the Arab raids into Central Asia became more organized and his lieutenant governor of Khurasan, al-Hakam ibn Amr al-Ghifari, crossed the Oxus and raided Chaghaniyan in 667. His successor Rabi ibn Ziyad al-Harithi also launched an expedition into the region. According to H. A. R. Gibb, the expeditions against Chaghaniyan and other areas east of the Oxus river seemingly indicated “a methodical plan of conquest” of Soghdiana by Ziyad. In 705, the Arab general Qutayba ibn Muslim managed to make the Chaghan Khudah, whose name is mentioned as Tish, acknowledge Umayyad authority. The real reason for Tish's submission, however, was to gain aid in defeating the local rulers of Akharun and Shuman in northern Tokharistan, who had been making incursions against him. Qutayba shortly defeated the two rulers, and forced them to acknowledge Umayyad authority.

However, in 718, Tish, along with Gurak, the king of Samarkand, Narayana, the king of Kumadh, and Tughshada, the Bukhar Khudah of Bukhara, sent an embassy to the Tang dynasty of China, where they asked for aid against the Arabs. Nevertheless, the principality of Chaghaniyan still aided the Arabs against the Turgesh, and were present at the side of the Arabs during the Battle of the Baggage, where they were defeated and the Chaghan Khudah was killed. After the battle, most of Khorasan except Chaghaniyan remained under Arab control. Under Nasr ibn Sayyar, Chaghaniyan was once again a vassal of the Umayyad Caliphate. After this, the Chaghan Khudahs begin to fade from the sources. In the late 8th-century Chaghaniyan fell under the direct control of the Abbasid Caliphate, which had succeeded the Umayyad Caliphate in 750. The Muhtajids, an Iranian dynasty which in the 10th-century gained control over Chaghaniyan, may have been descended from the Chaghan Khudahs.

The founder of the Muhtajid dynasty was Abu Bakr Muhammad, who was a vassal of the Samanids, another Iranian dynasty. He was a loyal supporter of the Samanid ruler Nasr II (914–943), who in return, rewarded him by appointing him as the governor of Khorasan. In 939, Abu Bakr Muhammad fell ill and was replaced from his post by his son Abu 'Ali Chaghani.