The Khurramites (Persian: خرمدینان Khorrām-Dīnān, meaning "those of the Joyful Religion"; Arabic: خُرَّمِيَة Khurramiyya) were an Iranian religious and political movement with its roots in the movement founded by Mazdak. An alternative name for the movement is the Muḥammira (Arabic: محمرة, "Red-Wearing Ones"; in Persian: سرخجامگان Surkh-Jāmagān), a reference to their symbolic red dress.
The sect was founded by the Persian cleric Sunpadh and was a revitalization of an earlier sect that had mixed Shī‘a Islam and Zoroastrianism; however, its true claim to fame was its adoption by Bābak Khorramdin as a basis for rebelling against the Abbasid Caliphate.
The sect grew out of a response to the execution of Abu Muslim by the Abbasids, and denied that he had died, rather claiming that he would return as the messiah. This message was further confirmed by the appearance of a prophet named al-Muqanna‘ "The Veiled", who claimed that the spirit of God had existed in Muhammad, ‘Alī and Abu Muslim.
Under the leadership of Bābak, the Khurammites proclaimed the breakup and redistribution of all the great estates and the end to despotic foreign rule. Taking advantage of the turmoil created by the Abbasid civil war, in 816 they began making attacks on Muslim forces in Iran and Iraq. The Abbasid suppression of the rebellion led to the flight of many thousand Khurramites to Byzantium, where they were welcomed by emperor Theophilos and enrolled in the Byzantine army under their Iranian leader, Theophobos.