The local population, made up of Qataris, are all Muslims although there are high numbers of foreign workers in Qatar which varies the Muslim population. In the CIA World Factbook it says 77.5% are Muslims, with 8.5% Christians and others remain. Foreign workers are well noted in the country, mainly from South Asia and Americans which constitute most of the population of Qatar.
Islam conquered the entire Arabian region in the 7th century in a string of widespread conflicts resulting in the Islamization of the native Arabian pagans. With the spread of Islam in Qatar, Muhammad sent his first military envoy, Al Ala Al-Hadrami, to Al-Mundhir Ibn Sawa Al-Tamimi, the ruler of Bahrain, which extended from the coast of Kuwait to the south of Qatar, including Al-Hasa and Bahrain, in the year 628, inviting him to accept Islam as he had invited other kingdoms and empires of his time such as Byzantium and Persia. Mundhir, responding to Muhammad, announced his acceptance of Islam, and all the inhabitants of Qatar became Muslim, heralding the beginning of the Islamic era in Qatar.