Wahhabism (Arabic: الوهابية‎, al-Wahhābiya(h)) is an Islamic doctrine and religious salafi movement founded by Muhammad ibn Abd al-Wahhab.^[1] It has been variously described as "ultraconservative",^[2] "austere",^[3] "fundamentalist",^[4] or "puritan(ical)";^[5][6] as an Islamic "reform movement" to restore "pure monotheistic worship" (tawhid) by devotees;^[7] and as a "deviant sectarian movement",^[7] "vile sect"^[8] and a distortion of Islam by its opponents.^[3][9]The term Wahhabi(ism) is often used polemically and adherents commonly reject its use, preferring to be called Salafi or muwahhid.^[10][11][12] claiming to emphasize the principle of tawhid^[13] (the "uniqueness" and "unity" of God),^[14] for exclusivity on monotheism, dismissing other Muslims as practising shirk, (idolatry).^[15] It follows the theology of Ibn Taymiyyah and the Hanbali school of jurisprudence, although Hanbali leaders renounced Abd al-Wahhab's views.^[6]

Wahhabism is named after an eighteenth-century preacher and activist, Muhammad ibn Abd al-Wahhab (1703–1792).^[16] He started a reform movement in the remote, sparsely populated region of Najd,^[17] advocating a purging of such widespread Sunni practices as the veneration of saints and the visiting of their tombs and shrines, that were practiced all over the Islamic world, but which he considered idolatrous impurities and innovations in Islam (Bid'ah).^[18][14] Eventually he formed a pact with a local leader, Muhammad bin Saud, offering political obedience and promising that protection and propagation of the Wahhabi movement meant "power and glory" and rule of "lands and men".^[19]

The alliance between followers of ibn Abd al-Wahhab and Muhammad bin Saud's successors (the House of Saud) proved to be a durable one. The House of Saud continued to maintain its politico-religious alliance with the Wahhabi sect through the waxing and waning of its own political fortunes over the next 150 years, through to its eventual proclamation of the Kingdom of Saudi Arabia in 1932, and then afterwards, on into modern times. Today Ibn Abd Al-Wahhab's teachings are the official, state-sponsored form of Sunni Islam^[3][20] in Saudi Arabia.^[21] With the help of funding from Saudi petroleum exports^[22] (and other factors^[23]), the movement underwent "explosive growth" beginning in the 1970s and now has worldwide influence.^[3] The US State Department has estimated that over the past four decades concerns in Riyadh (a global city) have directed at least $10bn (£6bn) to select charitable foundations toward the subversion of mainstream Sunni Islam by the harsh intolerance of Wahhabism.^[24] (as of 2017 changes to Saudi religious policy by Crown Prince Muhammad bin Salman have led some to suggest that "Islamists throughout the world will have to follow suit or risk winding up on the wrong side of orthodoxy".^[25])

The "boundaries" of Wahhabism have been called "difficult to pinpoint",^[26] but in contemporary usage, the terms Wahhabi and Salafi are often used interchangeably, and they are considered to be movements with different roots that have merged since the 1960s.^[27][28][29] However, Wahhabism has also been called "a particular orientation within Salafism",^[30] or an ultra-conservative, Saudi brand of Salafism.^[31][32] Estimates of the number of adherents to Wahhabism vary, with one source (Mehrdad Izady) giving a figure of fewer than 5 million Wahhabis in the Persian Gulf region (compared to 28.5 million Sunnis and 89 million Shia).^[21][33]

The majority of Sunni and Shia Muslims worldwide disagree with the interpretation of Wahhabism, and many Muslims denounce them as a faction or a "vile sect".^[8] Islamic scholars, including those from the Al-Azhar University, regularly denounce Wahhabism with terms such as "Satanic faith".^[34] Wahhabism has been accused of being "a source of global terrorism",^[35][36] inspiring the ideology of the Islamic State of Iraq and the Levant (ISIL),^[37]and for causing disunity in Muslim communities by labelling Muslims who disagreed with the Wahhabi definition of monotheism as apostates^[38] (takfir) and justifying their killing.^[39][40][41]It has also been criticized for the destruction of historic shrines of saints, mausoleums, and other Muslim and non-Muslim buildings and artifacts.^[42][43][44]