Abdullah bin Abdulaziz Al Saud (Arabic: Abd Allh ibn Abd al Azz l Sad, Najdi Arabic pronunciation: [bd. ben bdl ziz l sud]; 1 August 1924 23 January 2015) was King and Prime Minister of Saudi Arabia from 1 August 2005 until his death in 2015. Prior to his ascension, he was Crown Prince of Saudi Arabia since 13 June 1982. He was the tenth son of King Abdulaziz, the founder of Saudi Arabia, and the fifth of Abdulaziz's six sons who were kings.

Abdullah was the son of King Abdulaziz and Fahda bint Asi Al Shuraim. His mother was a member of the Al Rashid dynasty, historical rivals of the Al Saud dynasty. Abdullah held important political posts throughout most of his adult life. In 1961 he became mayor of Mecca, his first public office. The following year, he was appointed commander of the Saudi Arabian National Guard, a post he was still holding when he became king. He also served as deputy defense minister and was named crown prince when his half-brother Fahd took the throne in 1982. After King Fahd suffered a serious stroke in 1995, Abdullah became the de facto ruler of Saudi Arabia until ascending the throne a decade later.

During his reign, Abdullah maintained close relations with the United States and the United Kingdom and bought billions of dollars worth of defense equipment from both states. He also gave women the right to vote for municipal councils and to compete in the Olympics. Abdullah maintained the status quo when there were waves of protest in the kingdom during the Arab Spring. According to a 2013 BBC report, Saudi Arabia could obtain nuclear weapons at will from Pakistan during Abdullah's reign due to the close relations between the two countries. The King had a longstanding relationship with Pakistan, and brokered a compromise between General Pervez Musharraf and ousted Prime Minister Nawaz Sharif, whom he had requested to be exiled to Saudi Arabia for a 10-year exile, following his ouster in the 1999 Pakistani coup d'tat.The three crown princes during Abdullah's reign were among the full brothers of King Fahd. Upon becoming king in 2005, Abdullah appointed his half-brother Sultan bin Abdulaziz as crown prince. When Sultan died in 2011, Sultan's full brother Nayef was named heir to the throne, but Nayef himself died the next year. Abdullah then named Salman bin Abdulaziz as crown prince. According to various reports, the King married up to 30 times and had more than 35 children. He was among the wealthiest royals in the world. Upon his death in 2015 at age 90, Abdullah was succeeded by his half-brother Salman.

The Allegiance Council (Arabic: هيئة البيعة Hay’at al-Bay‘ah), also known as the Allegiance Commission or Allegiance Institution, is the body responsible for determining future succession to the throne of Saudi Arabia. It was formed on 7 December 2007 by King Abdullah. At the time of its formation, the Council's intended function was to appoint a Crown Prince once a new King succeeds to the throne.