Islam is the national religion of Iraq, adhered to by some 97% of the population according to a 1997 census. About 60–65% of Muslims belong to the Shi'a sect and 32–37% to the Sunni sect. Traditionally, the Shi'a majority has been governed and generally oppressed by members of the Sunni minority, which since the late 1970s has become increasingly concerned about the export of Shi'a militancy from Iran. There are also some syncretic Muslim groups, such as the Yazidis, who consider Satan a fallen angel who will one day be reconciled with God. They propitiate him in their rites and regard the Old and New Testaments, as well as the Koran (Qur'an), as sacred.
About 3% of the population are adherents to Christianity and other religions. More than 500,000 of the Christians were Roman Catholic, and nearly all the remainder belonged to various branches of Oriental Christianity. The Assyrians (who are not descended from the ancient Assyrians) are Nestorians. In the 19th century, under the influence of Roman Catholic missions, Christian Chaldaeans, originally also Nestorians, joined the Uniate churches, which are in communion with Rome; their patriarch has his seat in Mosul. The Sabaeans, or Mandaeans, are often called Christians of St. John, but their religious belief and their liturgy contain elements of many creeds, including some of pre-Christian Oriental origin. Since baptism is their main ritual, they always dwell near water and are concentrated on the riverbanks south of Baghdad. Iraq's Jewish community, which had its origins in Babylonian times and which produced outstanding scholars during the first millennium AD , dwindled from about 90,000 in 1948 to 200 in 1990, virtually all Iraqi Jewry having emigrated to Israel by the early 1950s.