Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī (1058–1111) (Persian: ابو حامد محمد ابن محمد الغزالی‎), known as Al-Ghazali or Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia (modern day Iran) was a Persian Muslim theologian, jurist, philosopher, and mystic.

Ghazali has sometimes been referred to by historians as the single most influential Muslim after the Islamic prophet Muhammad. Others have cited his movement from science to faith as a detriment to Islamic scientific progress. Besides his work that successfully changed the course of Islamic philosophy—the early Islamic Neoplatonism developed on the grounds of Hellenistic philosophy, for example, was so successfully refuted by Ghazali that it never recovered—he also brought the orthodox Islam of his time in close contact with Sufism. The orthodox theologians still went their own way, and so did the mystics, but both developed a sense of mutual appreciation which ensured that no sweeping condemnation could be made by one for the practices of the other.