Wahhabism, a peculiar interpretation of Islamic doctrine and practice that first arose in mid-eighteenth century Arabia, is sometimes regarded as simply an extreme or uncompromising form of Sunni Islam. This is incorrect, for at the very outset the movement was stigmatized as aberrant by the leading Sunni scholars of the day, because it rejected many of the traditional beliefs and practices of Sunni Islam and declared permissible warfare against all Muslims that disputed Wahhabi teachings. Nor can Wahhabism be regarded as a movement of “purification” or “renewal,” as the source of the genuinely revivalist movements that were underway at the time. Not until Saudi oil money was placed at the disposal of its propagandists did Wahhabism find an echo outside the Arabian Peninsula. The author discusses the rise of Wahhabism at the hands of Muhammad b. ‘Abd al-Wahhab, a native of Najd in the eastern part of the Arabian peninsula, the doctrines he elaborated to serve as the basis of the Wahhabi sect, and the alliance he concluded with the Saudi family, then rulers of the principality of al-Dir’iya. An early result of this union was a creeping conquest of the Arabian Peninsula, misnamed as jihad; it culminated in the sacking of Taif and the occupation of Mecca in 1803. This first Wahhabi occupation was short-lived but Wahhabism triumphed anew with the foundation of the Kingdom of Saudi Arabia in 1925. Among the extensions of Wahhabism beyond Arabia must be accounted the perverse and brutal regime of the Taliban in Afghanistan.