Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the center of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about 2,150,000 km (830,000 sq mi), making it the fifth-largest country in Asia, the largest in the Middle East, and the twelfth-largest in the world. It is bordered by the Red Sea to the west; Jordan, Iraq, and Kuwait to the north; the Persian Gulf, Bahrain, Qatar and the United Arab Emirates to the east; Oman to the southeast; and Yemen to the south. The Gulf of Aqaba in the northwest separates Saudi Arabia from Egypt and Israel. Saudi Arabia is the only country with a coastline along both the Red Sea and the Persian Gulf, and most of its terrain consists of arid desert, lowland, steppe, and mountains. The capital and largest city is Riyadh; other major cities include Jeddah and the two holiest cities in Islam, Mecca and Medina. With a population of almost 32.2 million, Saudi Arabia is the fourth most populous country in the Arab world.
Pre-Islamic Arabia, the territory that constitutes modern-day 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 outside Africa. Islam emerged in what is now Saudi Arabia in the early seventh century. Islamic prophet Muhammad united the population of the Arabian Peninsula and created a single Islamic religious polity. Following his death in 632, his followers expanded Muslim rule beyond Arabia, conquering territories in North Africa, Central, South Asia and Iberia within 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 Muslim states in Asia, Africa, and Europe.