Until Bahrain embraced Islam in AD 629, it was a center for Nestorian Christianity. Among its inhabitants, the major tribe was the Abdul Qais.
In the early 7th century, Bahrain was one of the first places in Arabia to become Islamic, despite its great distance from Muhammad's base in Medina.
In 899 the Qarmatians, a millenarian Ismaili sect, seized hold of the country and sought to create a utopian society based on reason and the distribution of all property evenly among the initiates. The Qarmatians caused widespread disruption throughout the Islamic world and sacked Mecca and Medina in 930, carrying off the sacred Black Stone to Qatif where it was held for ransom. They were defeated in 976 by the Abbasids.
The name "Bahrain" referred to the eastern mainland Arabia until the 16th century at least. The Arab inhabitants of the province, were called Bahrani's after it.