Over 99% of the people in Afghanistan are Muslim.
Islam is Afghanistan’s dominant religion and its official state religion. Most Afghan Muslims are Sunni Muslims who traditionally follow the Hanafi school of Islamic jurisprudence. A substantial minority are Shia Muslims, including many members of the Hazara community; smaller groups follow Ismaili traditions.
Islam reached the region gradually after the Arab Muslim conquests beginning in the seventh century. Conversion continued over several centuries, as Islam became established alongside and eventually largely replaced older religious traditions, including Buddhism and Zoroastrianism. The Ghaznavid period later helped spread Islamic institutions and culture across much of the region.
The wording can cause a small grammatical mix-up: Islam is the name of the religion, while Muslim describes a person who follows it. In ordinary trivia usage, however, “Muslim” is the expected answer because the question asks what the people belong to. Afghanistan’s religious majority is especially notable because Sunni and Shia communities coexist within the country, despite political and sectarian tensions.