The death of Muhammad and the Arab-Muslim conquests opened a new era in Middle Eastern civilizations. The Arab-Muslim conquests initiated the long historical process that culminated in the amalgamation of Arabia, the Sasanian Empire, and the eastern regions of the Byzantine Empire within an Islamic empire; in the eventual conversion of the majority of Jewish, Christian, and Zoroastrian peoples to Islam; and in the formation of an Islamic society and culture.

On Muhammad's death, many of his followers decided on the appointment of a caliph or executor of the Prophet's legacy. The first four caliphs – Abu Bakr (632–34), ʿUmar (634–44), ʿUthman (644–56), and ʿAli (656–61) – ruled by virtue of their personal connections with Muhammad and Arabian ideas of authority. They were later called the Rashidun, the Rightly Guided Caliphs. These caliphs, in part following the precedents set by Muhammad, launched a great wave of military campaigns and a migration of Arabian peoples leading to the conquest of all the lands of the former Sasanian Empire and the Near Eastern and North African provinces of the Byzantine Empire. Iraq, Syria, and Egypt were conquered by 641; Iran by 654. North Africa was conquered between 643 and 711; Spain between 711 and 759. In the east, the region of Inner Asia between the Oxus and the Jaxartes rivers, Transoxania, was fully conquered by 751. Thus, the “Middle East,” North Africa, Spain, and Transoxania were incorporated into a single empire. The Islamic religion and related cultures and an Islamic sociopolitical identity would be formed in this region.