/div>Country, Middle East, southwestern Asia. It occupies four-fifths of the Arabian Peninsula
and is bounded by the Red Sea and the Persian Gulf. Area: 830,000 sq mi (2,149,690 sq km). Population: (2009 est.) 25,316,000. Capital: Riyadh
. The people are predominantly Arab. Language: Arabic (official). Religion: Islam (official; predominantly Sunni). Currency: Saudi riyal. The country is a plateau region, with bands of imposing highlands rising from the narrow Red Sea coast. More than nine-tenths is desert, including the world's largest continuous sand area, the Rub' al-Khali
(Empty Quarter). The largest petroleum producer of the Organization of Petroleum Exporting Countries
(OPEC) and one of the leading oil exporters in the world, Saudi Arabia has reserves that represent one-fourth of the world total. Its other products include natural gas, gypsum, dates, wheat, and desalinated water. It is a monarchy; its head of state and government is the king, assisted by the crown prince. Saudi Arabia is the historical home of Islam
. During premodern times, local and foreign rulers fought for control of the region; in 1517 the Ottoman Empire attained nominal control of most of the peninsula. In the 18th–19th century an Islamic reform group known as the Wahhabi
joined with the Sa'ud dynasty
to take control of most of central Arabia; they suffered political setbacks but regained most of their territory by 1904. The British held Saudi lands as a protectorate (1915–27), after which they acknowledged the sovereignty of the Kingdom of the Hejaz and Nejd. The two kingdoms were unified as the Kingdom of Saudi Arabia in 1932. Since World War II (1939–45), the kingdom's rulers have supported the Palestinian cause in the Middle East and maintained close ties with the U.S. In 2000 Saudi Arabia and Yemen settled a long-standing border dispute.