The Indo-Sassanids, Kushano-Sassanids or Kushanshas (also Indo-Sassanians) were a branch of the Sassanid Persians who established their rule in the northwestern Indian subcontinent during the third and fourth centuries CE at the expense of the declining Kushans. They were in turn displaced in 410 CE by the invasions of the Indo-Hephthalites. They were able to re-establish some authority after the Sassanids destroyed the Hephthalites in 565 CE, but their rule collapsed under Arab attacks in the mid 600s.
The Sassanids, shortly after their victory over the Parthians, extended their dominion into Bactria during the reign of Ardashir I around 230 CE, then further to the eastern parts of their empire (modern Pakistan and India) during the reign of his son Shapur I (240-270). Thus the Kushans lost their western territory (including Bactria and Gandhara) to the rule of Sassanid nobles named Kushanshahs or "Kings of the Kushans".
Kartir, a high-priest that served as advisor to at least three of the early kings, instigated the persecution of non-Zoroastrians, that is, Christians, Buddhists, Jews, Hindus and - in particular - the Manichaeans, who were primarily in and from the eastern territories. The persecution ceased during the reign of Narseh (r. 293–302).
Around 325, Shapur II was directly in charge of the southern part of the territory, while in the north the Kushanshahs maintained their rule until the rise of the Kidarites.
The decline of the Kushans and their defeat by the Sassanids led to the rise of an indigenous Indian dynasty, the Guptas, in the fourth century. In 410 the Hephthalites or Indo-Hephthalites conquered Bactria and Gandhara, thus temporarily replacing the Indo-Sassanids.
On that occasion, various Buddhist influences seem to have permeated Manichaeism: "Buddhist influences were significant in the formation of Mani's religious thought. The transmigration of souls became a Manichaean belief, and the quadripartite structure of the Manichaean community, divided between male and female monks (the 'elect') and lay follower (the 'hearers') who supported them, appears to be based on that of the Buddhist sangha" (Richard Foltz, Religions of the Silk Road).
The Indo-Sassanids created an extensive coinage with legend in Brahmi, Pahlavi or Bactrian, sometimes inspired from Kushan coinage, and sometimes more clearly Sassanid.
The obverse of the coin usually depicts the ruler with elaborate headdress and on the reverse either the zoroastrian fire altar or Shiva and his bull Nandi.