Apart from a brief invasion in 616, Egypt remained under Byzantine rule until the advance of Islam in the seventh century. Led by the Prophet Mohammed's successor, Abu Bakr, the Muslim armies defeated the Byzantine army in 636. General Amr Ibn al-As then advanced towards Babylon-in-Egypt, which surrendered after a brief siege, to be followed by Heliopolis (640) and finally the imperial capital of Alexandria (642).

 

Amr built his capital, Fustat , north of the fortress town of Babylon-in-Egypt, in what is today Old Cairo. However, Egypt was merely a province in the vast Islamic empire that was governed from Damascus and Baghdad. As in Roman times, Egypt's primary role was as a bread basket for the empire.

Arabization and Islamicization was a gradual and uneven process, with intermittent periods of religious toleration and discrimination. Much depended on the character of the khalifs, and their own power struggles, whose impact was felt throughout the Islamic empire. In 750, the empire's ruling Umayyad dynasty was defeated by the armies of Abu al-Abbas (a descendant of Abu Bakr) and an Abbasid khalifate came to power in Baghdad, administering Egypt, along with its other territories, for the next two centuries.