Saudi Arabia, monarchy in southwestern Asia, occupying most of the Arabian Peninsula. Saudi Arabia is a land of vast deserts and little rainfall. Huge deposits of oil and natural gas lie beneath the country’s surface. Saudi Arabia was a relatively poor nation before the discovery and exploitation of oil, but since the 1950s income from oil has made the country wealthy. The religion of Islam developed in the 7th century in what is now Saudi Arabia. The Kingdom of Saudi Arabia was founded in 1932 by Abdul Aziz ibn Saud, and it has been ruled by his descendants ever since.