Abdulaziz bin Abdul Rahman Al Saud (Arabic: عبد العزيز بن عبد الرحمن آل سعود, romanized: ʿAbd al ʿAzīz bin ʿAbd ar Raḥman Āl Suʿūd; 15 January 1875 – 9 November 1953), known in the West as Ibn Saud (Arabic: ابن سعود Ibn Suʿūd), was an Arab tribal, political, and religious leader who founded Saudi Arabia, the third Saudi state. He reigned as the first king of Saudi Arabia from 23 September 1932 to his death in 1953. He had ruled parts of the kingdom since 1902, having previously been Emir, Sultan, and King of Nejd, and King of Hejaz.

Ibn Saud was the son of Abdul Rahman bin Faisal, Emir of Nejd, and Sara bint Ahmed Al Sudairi. The family were exiled from their residence in the city of Riyadh in 1890. Ibn Saud reconquered Riyadh in 1902, starting three decades of conquests that made him the ruler of nearly all of central and north Arabia. He consolidated his control over the Nejd in 1922, then conquered the Hejaz in 1925. He extended his dominions into what later became the Kingdom of Saudi Arabia in 1932. As King, he presided over the discovery of petroleum in Saudi Arabia in 1938 and the beginning of large-scale oil production after World War II. He fathered many children, including 45 sons, and all of the subsequent kings of Saudi Arabia.