The Wahhabi sack of Karbala occurred on 21 April 1802 (1216 H), under the rule of Abdulaziz bin Muhammad the second ruler of the First Saudi State. Approximately 12,000 Wahhabis from Najd attacked the city of Karbala.:387 The raid was conducted in retaliation against attacks on Hajj caravans by Iraqi tribes and coincided with the anniversary of Ghadir Khum event, or 10th Muharram.:74Wahhabis killed 2,000:745,000 of the inhabitants and plundered the tomb of Husayn ibn Ali, grandson of Prophet Muhammad and son of Ali ibn Abi Talib,:74 and destroyed its dome, seizing a large quantity of spoils, including gold, Persian carpets, money, pearls, and guns that had accumulated in the tomb, most of them donations. The attack lasted for eight hours, after which the Wahhabis left the city with more than 4,000 camels carrying their plunder.

Wahhabism (Arabic: الوهابية, romanized: al-Wahhābiyyah) is a Sunni revivalist and fundamentalist movement associated with the Hanbali reformist doctrines of the 18th-century Arabian Islamic scholar, theologian, preacher, and activist Muhammad ibn Abd al-Wahhab (c. 1703–1792). He established the Muwahhidun movement in the region of Najd in central Arabia, a reform movement with a particular emphasis on purging practices such as the veneration of Muslim saints and pilgrimages to their tombs and shrines, which were widespread amongst the people of Najd. Ibn ʿAbd al-Wahhab and his followers were highly inspired by the influential thirteenth-century Hanbali scholar Ibn Taymiyyah (1263–1328 C.E/ 661 – 728 A.H) who called for a return to the purity of the first three generations (Salaf) to rid Muslims of inauthentic outgrowths (bidʻah), and regarded his works as core scholarly references in theology. While being influenced by their Hanbali doctrines, the movement repudiated Taqlid to legal authorities, including oft-cited scholars such as Ibn Taymiyya and Ibn Qayyim (d. 1350 C.E/ 751 A.H).Wahhabism has been variously described as "orthodox", "puritan(ical)"; and as an Islamic "reform movement" to restore "pure monotheistic worship" by devotees. The term "Wahhabism" was not used by Ibn 'Abd al-Wahhab himself, but is chiefly used by outsiders, while adherents typically reject its use, preferring to be called "Salafi" (a term also used by followers of other Islamic reform movements as well). The movement's early followers referred to themselves as Muwahhidun (Arabic: الموحدون, lit. '"one who professes God's oneness" or "Unitarians"' derived from Tawhid (the oneness of God). The term "Wahhabism" is also used as a sectarian or Islamophobic slur. Adherents of Wahhabism follow the Athari school of Islamic theology.

In 1744, Ibn ʿAbd al-Wahhab formed a pact with a local leader, Muhammad bin Saud, a politico-religious alliance that continued for the next 150 years, culminating politically with the proclamation of the Kingdom of Saudi Arabia in 1932. For more than two centuries through to the present, Ibn ʿAbd al-Wahhab's teachings were championed as the official form of Islam and the dominant creed in three Saudi States. 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".In 2018 Saudi Crown Prince Mohammed bin Salman, denied that anyone "can define this Wahhabism" or even that it exists. By 2021, the waning power of the religious clerics brought forth by the social, religious, economic, political changes and a new educational policy asserting a "Saudi national identity" that emphasize non-Islamic components have led to what has been described as the "post-Wahhabi era" of Saudi Arabia. By 2022, the decision to celebrate the "Saudi Founding Day" annually on 22 February to commemorate the 1727 establishment of Emirate of Dir'iyah by Muhammad ibn Saud, rather than the past historical convention that traced the beginning to the 1744 pact of Ibn 'Abd al-Wahhab; have led to the official "uncoupling" of the religious clergy by the Saudi state.