In pre-Islamic times, apart from a small number of urban trading settlements (such as Mecca and Medina), most of what was to become Saudi Arabia was populated by nomadic tribal societies in the inhospitable desert.[38] The Islamic prophet, Muhammad, was born in Mecca in about 571 A.D. In the early 7th century, Muhammad united the various tribes of the peninsula and created a single Islamic religious polity. Following his death in 632, his followers rapidly expanded the territory under Muslim rule beyond Arabia, conquering huge swathes of territory (from the Iberian Peninsula in west to modern day Pakistan in east) in a matter of decades. In so doing, Arabia soon became a politically peripheral region of the Muslim world as the focus shifted to the more developed conquered lands.[39] From the 10th century to the early 20th century Mecca and Medina were under the control of a local Arab ruler known as the Sharif of Mecca, but at most times the Sharif owed allegiance to the ruler of one of the major Islamic empires based in Baghdad, Cairo or Istanbul. Most of the remainder of what became Saudi Arabia reverted to traditional tribal rule.[40][41]

In the 16th century, the Ottomans added the Red Sea and Persian Gulf coast (the Hejaz, Asir and Al-Ahsa) to the Empire and claimed suzerainty over the interior. One reason was to thwart Portuguese attempts to attack the Red Sea (hence the Hejaz) and the Indian Ocean.[42] Ottoman degree of control over these lands varied over the next four centuries with the fluctuating strength or weakness of the Empire's central authority.[43][44] The emergence of what was to become the Saudi royal family, known as the Al Saud, began in Nejd in central Arabia in 1744, when Muhammad bin Saud, founder of the dynasty, joined forces with the religious leader Muhammad ibn Abd al-Wahhab,[45] founder of the Wahhabi movement, a strict puritanical