Religion of Persia, popular in the 5th and 6th centuries, and surviving until the 8th century. Mazdakism was a movement that also had great political implications, causing a social revolution and rebellion around 600.
The founder of the group was Mazdak of Fesa (died 524 or 528), who started preaching his new religious concepts sometime around 484, a year of much suffering in the Sassanid Empire. It is usually assumed that Mazdak himself was originally a Zoroastrian priest, mobed, but his teaching had its roots in other contemporary religions too, where Manichaeism appears to have been the most important.
Cosmology and Theology
Mazdakism share the dualistic cosmology/theology with Manichaeism. There were two original principles of the universe: Light, the good one; and Darkness, the evil one. These two had been mixed by a cosmic accident, and man's role in this life was through good conduct to release the parts of himself that belonged to Light. But where Manichaeism saw the mixture of good and bad as a cosmic tragedy, Mazdak viewed this in a more neutral, even optimistic way. Mazdak preached that the mix of good and evil had touched everything, including God.
The two distinguishing factors in Mazdak's teaching was to reduce the importance of religious formalities, claiming that the true religious person was one who understood and related correctly to the principles of the universe; and a criticism of the strong position of Zoroastrian clergy which had resulted in suppression of the Persian population and much poverty. In many ways can Mazdak's teaching be understood as a call for social revolution, and he has been called the "first Socialist in history".
Mazdak emphasized good conduct, which involved a moral and ascetic life, no killing and not eating flesh (which contained substances solely from Darkness), being kind and friendly and live in peace with other people.
Despite the concepts of good conduct, the followers of Mazdak raided the palaces and harems of the rich, removing the valuables they believed they had equal rights on. Facing the unrest in the empire, the King Kavadh 1, ruling from 488 until 531, converted to Mazdakism. With his backing could Mazdak embark on a program of social reform, which involved pacifism, anti-clericalism and aid programs for helping the poor. Mazdak had government warehouses opened to help the poor in the society. Mazdak had most Zoroastrian fire temples closed, save 3.
His programs were so dramatic that there rumours told that he planned to have all private property confiscated, and replace marriage with free sex.
Fear from among the nobles and Zoroastrian clergy grew so strong that Kavadh was overthrown in 496, but he managed to get the throne back 3 years later with the help of the Hephthalites. Scared by the resistance among the powerful, he chose to distance himself from Mazdak. He allowed his son and crown prince Khosrau to launch a great campaign against the Mazdakis in 524 or 528, culminating in a massacre killing most of the adherents, including Mazdak himself and Kavadh's oldest son. Some survived, and settled in remote areas. Small pockets of Mazdaki societies survived for centuries, but eventually be absorbed by Central Asian Buddhism.
We have no direct sources of Mazdakism, none of their books have survived. Our knowledge is made up of brief mentions in Syrian, Persian, Arabic and Greek sources, and much of the information is written by opponents of Mazdakism.