Wahhabism is a reformist movement within Sunni Islam, based on the teachings of 18th century Hanbali cleric Muhammad ibn Abd al-Wahhab. The term "Wahhabism" is primarily an exonym (name used by outsiders); it was not used by Ibn Abd al-Wahhab himself or adherents to the movement, who typically prefer to be called "Salafi" (a term also used by followers of other Islamic reform movements). The movements early followers referred to themselves as Muwahhidun, which means "unitarians" in Arabic.

Wahhabism is characterized by its emphasis on the absolute oneness of God (tawḥīd) and its rejection of acts that are viewed as polytheistic. It is an austere form of Islam that insists on a literal interpretation of the Quran. Critics say that Wahhabisms rigidity has led it to misinterpret and distort Islam, pointing to extremists such as Osama bin Laden and the Taliban.

The term "Wahhabi" is used primarily by outsiders to distinguish the movement; adherents often refer to themselves as Salafis, which means "followers of the pious forebears". The Wahhabi movement was encouraged by the emir, Muhammad ibn Saud, and the political fortunes of the Wahhabi movement were closely allied to those of the Saudi dynasty. The activities of Ibn Saud in the 20th century eventually led to the creation of the Kingdom of Saudi Arabia in 1932 and assured Wahhabi religious and political dominance on the Arabian Peninsula.

It is important to note that the term "Wahhabi" has been commonly invoked by various external observers to erroneously or pejoratively denote a wide range of reform movements across the Muslim world. Despite sharing little resemblance with the doctrines of Ibn ʿAbd al-Wahhab, outside observers of the Muslim world have frequently traced various religious purification campaigns across the Islamic World to Wahhabi influence.