Qadariyah (or Qadariya) is an originally derogatory term designating early Islamic theologians who asserted that humans possess free will, whose exercise makes them responsible for their actions, justifying divine punishment and absolving God of responsibility for evil in the world. Some of their doctrines were later adopted by the Mu'tazilis and rejected by the Ash'aris.
Qadariya was one of the first philosophical schools in Islam. The earliest document associated with the movement is the Risala by Hasan al-Basri, which was composed between 75/694 and 80/699, though debates about free will in Islam probably predate this text.
According to Sunni sources, the Qadariyah were censured by Muhammad himself by being compared to Zoroastrians, who likewise deny predestination. It is reported in Sunan Abu Dawood: Narrated Abdullah ibn Umar: The Prophet said, "The Qadariyyah are the Magians of this community. If they are ill, do not pay a sick visit to them, and if they die, do not attend their funerals."
According to Zarinkoob, the notion of Qadariyah was issued by Ma'bad Juhāni (d. 699), who had adopted the views of an Iranian by the name Sanbuya, at the end of the Umayyad era.