The territory that now constitutes Saudi Arabia was the site of several ancient cultures and civilizations. The prehistory of Saudi Arabia shows some of the earliest traces of human activity in the world.
The area of modern-day Saudi Arabia formerly consisted of mainly four distinct regions: Hejaz, Najd and parts of Eastern Arabia (Al-Ahsa) and Southern Arabia ('Asir). The Kingdom of Saudi Arabia was founded in 1932 by Ibn Saud. He united the four regions into a single state through a series of conquests beginning in 1902 with the capture of Riyadh, the ancestral home of his family, the House of Saud. Saudi Arabia has since been an absolute monarchy, effectively a hereditary dictatorship governed along Islamist lines. The ultraconservative Wahhabi religious movement within Sunni Islam has been called "the predominant feature of Saudi culture", with its global spread largely financed by the oil and gas trade. Saudi Arabia is sometimes called "the Land of the Two Holy Mosques" in reference to Al-Masjid al-Haram (in Mecca) and Al-Masjid an-Nabawi (in Medina), the two holiest places in Islam. As of 2013, the state had a total population of 28.7 million, of which 20 million were Saudi nationals and 8 million were foreigners. As of 2017, the population is 33 million. The state's official language is Arabic.
Following the unification of the Hejaz and Nejd kingdoms, the new state was named al-Mamlakah al-ʻArabīyah as-Suʻūdīyah (a transliteration of المملكة العربية السعودية in Arabic) by royal decree on 23 September 1932 by its founder, Abdulaziz Al Saud (Ibn Saud). Although this is normally translated as "the Kingdom of Saudi Arabia" in English, it literally means "the Saudi Arab kingdom", or "the Arab Saudi Kingdom".
The word "Saudi" is derived from the element as-Suʻūdīyah in the Arabic name of the country, which is a type of adjective known as a nisba, formed from the dynastic name of the Saudi royal family, the Al Saud (Arabic: آل سعود). Its inclusion expresses the view that the country is the personal possession of the royal family.Al Saud is an Arabic name formed by adding the word Al, meaning "family of" or "House of", to the personal name of an ancestor. In the case of the Al Saud, this is the father of the dynasty's 18th-century founder, Muhammad bin Saud.