Mirza Ghulam Ahmad as the promised Messiah and Mahdi

Members of the Ahmadiyya movement affirm that its founder, Mirza Ghulam Ahmad of Qadian (1835-1908), was the Promised Messiah and the Mahdi awaited by Muslims, and, in the community's understanding, a subordinate prophet who brought no new law but revived Islam. They hold that he came to defend the faith by argument rather than the sword and to unite humanity under Islam. The community stresses that it affirms the finality of Muhammad's prophethood while interpreting Ghulam Ahmad's status as prophecy of a reflected, non-law-bearing kind. Ghulam Ahmad took his first pledge of allegiance from followers at Ludhiana in 1889, the date the movement counts as its founding, and developed his claims to be the Promised Messiah and Mahdi through the 1890s.

After his death in 1908 the movement split over exactly how to understand his status: the majority Qadiani branch, now headquartered in London and led by a hereditary caliph (khalifa), holds that Ghulam Ahmad was a true, if subordinate and non-law-bearing, prophet, while the smaller Lahori Ahmadiyya (Ahmadiyya Anjuman Isha'at-e-Islam), based in Lahore, holds that he was a reformer (mujaddid) and not a prophet in any sense, a distinction its members regard as essential to remaining fully within mainstream Islamic doctrine on the finality of prophethood.

This affirmation is the defining and most contested belief of the Ahmadiyya. The mainstream Sunni and Shia consensus holds that Muhammad is the final prophet in an absolute sense and therefore regards the claim as incompatible with Islam; several states have legislated on the question, and Ahmadis have faced persecution. This article describes the belief as the Ahmadiyya community holds and explains it, without adjudicating the theological dispute. It is inseparable from the community's further distinctive beliefs, including its account of the fate of Jesus.

The contestation has had severe legal consequences. Pakistan's parliament amended its constitution in 1974 to declare Ahmadis non-Muslim for the purposes of law, and Ordinance XX, issued by military ruler Zia-ul-Haq in 1984, made it a criminal offence for Ahmadis to call themselves Muslim, refer to their places of worship as mosques, or use Islamic terminology and practices in the ordinary way other Muslims do; violations can carry prison sentences, and Ahmadis have faced mob violence and targeted killings in Pakistan and elsewhere in the decades since. The community's own khalifa relocated its international headquarters from Rabwah, Pakistan, to London in 1984 in response to the ordinance, from where it continues to direct the worldwide Ahmadiyya Muslim Community today.