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.^[14] The world's second-largest religion,^[15] Islam, emerged in modern-day Saudi Arabia. In the early 7th century, the Islamic prophet Muhammad united the population of Arabia and created a single Islamic religious polity.^[16] Following his death in 632, his followers rapidly expanded the territory under Muslim rule beyond Arabia, conquering huge and unprecedented swathes of territory (from the Iberian Peninsula in the West to modern-day Pakistan in the East) in a matter of decades. Arab dynasties originating from modern-day Saudi Arabia founded the Rashidun (632–661), Umayyad (661–750), Abbasid (750–1517) and Fatimid (909–1171) caliphates as well as numerous other dynasties in Asia, Africa and Europe.^{[17][18][19][20][21]}

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).^[22] 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 a totalitarian absolute monarchy, effectively a hereditary dictatorship governed along Islamist lines.^{[23][24][25][26]} 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.^[23][24] 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. The state's official language is Arabic.

Petroleum was discovered on 3 March 1938 and followed up by several other finds in the Eastern Province.^[27] Saudi Arabia has since become the world's second largest oil producer (behind the US) and the world's largest oil exporter, controlling the world's second largest oil reserves and the sixth largest gas reserves.^[28] The kingdom is categorized as a World Bank high-income economy with a very high Human Development Index^[29] and is the only Arab country to be part of the G-20 major economies.^[30]

The state has attracted criticism for a variety of reasons including: its role in the Yemeni Civil War, sponsorship of Islamic terrorism, its failure to adopt adequate measures against human trafficking, and its poor human rights record, which has been characterized by the problematic treatment of women, excessive and often extrajudicial use of capital punishment, state-sponsored discrimination against religious minorities and atheists, state-sanctioned racism and antisemitism, and its strict interpretation of Shari'a law.^{[31][32][33][34][35][36][37][38]}

The kingdom spends 8% of its GDP on the military (highest in the world after Oman)^[39], which places it as the world's third biggest military spender behind the United States and China^[40], and the world's largest arms importer from 2015 to 2019, receiving half of all the US arms exports to the Middle East.^[41][42] According to the BICC, Saudi Arabia is the 28th most militarized country in the world and enjoys the region's best military equipment qualititively, after Israel.^[43] However, in recent years, there have been continuous calls for halting of arms sales to Saudi Arabia, mainly due to alleged war crimes in Yemen^[44] and especially following the assassination of Jamal Khashoggi.^[45][46]

Saudi Arabia is considered a regional and middle power.^[47] In addition to being a member of the Gulf Cooperation Council, it is an active and founding member of the United Nations, Organisation of Islamic Cooperation, Arab League, OPEC and is also a major non-NATO ally.^[48]