Wahhabi or Wahabi (wähä´bē), reform movement in Islam, originating in Arabia; adherents of the movement usually refer to themselves as Muwahhidun [unitarians]. It was founded by Muhammad ibn Abd al-Wahab (c.1703–1791), who was influenced by Ibn Taymiyya and taught that all accretions to Islam after the 3d cent. of the Muslim era—i.e., after c.950—were spurious and must be expunged. This view, involving essentially a purification of the Sunni sect, regarded the veneration of saints, ostentation in worship, and luxurious living as the chief evils. Accordingly, Wahhabi mosques are simple and without minarets, and the adherents dress plainly and do not smoke tobacco or hashish.
Driven from Medina for his preaching, the founder of the Wahhabi sect went into the NE Nejd and converted the Saud tribe. The Saudi sheik, convinced that it was his religious mission to wage holy war (jihad) against all other forms of Islam, began the conquest of his neighbors in c.1763. By 1811 the Wahhabis ruled all Arabia, except Yemen, from their capital at Riyadh. The Ottoman sultan, nominally suzerain over Arabia, had vainly sent out expeditions to crush them. Only when the sultan called on Muhammad Ali of Egypt for aid did he meet success; by 1818 the Wahhabis were driven into the desert.
In the Nejd the Wahhabis collected their power again and from 1821 to 1833 gained control over the Persian Gulf coast of Arabia. The domain thereafter steadily weakened; Riyadh was lost in 1884, and in 1889 the Saud family fled for refuge into the neighboring state of Kuwait. The Wahhabi movement was to enjoy its third triumph when Ibn Saud advanced from his capture of Riyadh in 1902 to the reconstitution in 1932 of nearly all his ancestral domain under the name Saudi Arabia, where it remains dominant. Wahhabism served as an inspiration to other Islamic reform movements from India and Sumatra to North Africa and Sudan, and during the 20th cent. has influenced the Taliban of Aghanistan and Islamist movements elsewhere.