Mazdak (Middle Persian: ) (died c. 524 or 528) (also Mazdak the Younger) was a Zoroastrian mobad (priest), Iranian reformer, prophet and religious activist who gained influence during the reign of the Sasanian emperor Kavadh I. He claimed to be a prophet of Ahura Mazda and instituted communal possessions and social welfare programs. He has been seen as a proto-socialist.
Mazdak was the chief representative of a religious and philosophical teaching called Mazdakism, which he viewed as a reformed and purified version of Zoroastrianism, although his teaching has been argued to display influences from Manichaeism as well. Zoroastrianism was the dominant religion of Sassanid Persia, and Mazdak himself was a mobad or Zoroastrian priest, but most of the clergy regarded his teaching as heresy. Information about it is scarce and details are sketchy, but some further details may be inferred from the later doctrine of the Khurramites, which has been seen as a continuation of Mazdakism.
Some sources claim that the original founders of this sect lived earlier than Mazdak. These were another mobad, Zaradust-e Khuragen (distinct from the founder of Zoroastrianism, Zoroaster, Middle Persian Zardusht) and/or a Zoroastrian philosopher known as Mazdak the Elder, who taught a combination of altruism and hedonism: "he directed his followers to enjoy the pleasures of life and satisfy their appetite in the highest degree with regard to eating and drinking in the spirit of equality, to aim at good deeds; to abstain from shedding blood and inflicting harm on others; and to practise hospitality without reservation". This doctrine was further developed by the much better-known Mazdak the Younger, son of Bāmdād.