theologian and founder of the Wahhābī movement, which attempted a return to the “true” principles of Islam.

Having completed his formal education in the holy city of Medina, in Arabia, ʿAbd al-Wahhāb lived abroad for many years. He taught for four years in Basra, Iraq, and in Baghdad he married an affluent woman whose property he inherited when she died. In 1736, in Iran, he began to teach against what he considered to be the extreme ideas of various exponents of Sufi (Ṣūfism) doctrines. On returning to his native city, he wrote the Kitāb at-tawḥīd (“Book of Unity”), which is the main text for Wahhābī doctrines. His followers call themselves al-Muwaḥḥidūn, or “Unitarians”; the term Wahhābī is generally used by non-Muslims and opponents.

ʿAbd al-Wahhāb's teachings have been characterized as puritanical and traditional, representing the early era of the Islamic religion. He made a clear stand against all innovations (bidʿah) in Islamic faith because he believed them to be reprehensible, insisting that the original grandeur of Islam could be regained if the Islamic community would return to the principles enunciated by the Prophet Muhammad. Wahhābī doctrines, therefore, do not allow for an intermediary between the faithful and Allah and condemn any such practice as polytheism. The decoration of mosques, the cult of saints, and even the smoking of tobacco were condemned.

When the preaching of these doctrines led to controversy, ʿAbd al-Wahhāb was expelled from ʿUyaynah in 1744. He then settled in Ad-Dirʿīyah, capital of Ibn Saʿūd, a ruler of the Najd (now in Saudi Arabia).

The spread of Wahhābīsm originated from the alliance that was formed between ʿAbd al-Wahhāb and Ibn Saʿūd, who, by initiating a campaign of conquest that was continued by his heirs, made Wahhābīsm the dominant force in Arabia since 1800.