Ali Abdullah Saleh (21 March 1947 – 4 December 2017) was a Yemeni military officer and politician who served as the first president of the Republic of Yemen from the Yemeni unification in 1990 until his resignation in 2012, following the Yemeni revolution. Previously, he had served as the fifth and last President of the Yemen Arab Republic (North Yemen), from July 1978 to 22 May 1990, after the assassination of President Ahmad al-Ghashmi. al-Ghashmi had earlier appointed Saleh as military governor in Taiz.

Saleh developed deeper ties with Western powers, especially the United States, during the War on Terror. Subsequently, evidence emerged that Islamic terrorism may have been used and encouraged by Ali Abdullah Saleh in order to win Western support and for disruptive politically motivated attacks. In 2011, in the wake of the Arab Spring, which spread across North Africa and the Middle East (including Yemen), Saleh's time in office became increasingly precarious, until he was eventually ousted as president in 2012. He was succeeded by Abdrabbuh Mansur Hadi, who had been serving as vice president since 1994, and acting president since 2011.

Himself a Zaydi Shia Muslim, Saleh openly allied with the Houthis (Ansar Allah) in May 2015 during the Yemeni civil war, in which a protest movement and subsequent insurgency succeeded in capturing Yemen's capital, Sanaa, causing President Hadi to resign and flee the country. In December 2017, he declared his withdrawal from his coalition with the Houthis and instead sided with his former enemies – Saudi Arabia, the United Arab Emirates and President al-Hadi.

On 4 December 2017, during a battle between Houthi and Saleh supporters in Sanaa, the Houthis accused Saleh of treason, and he was killed by a Houthi sniper. Reports were that Saleh was killed while trying to flee his compound in a car; however, this was denied by his party officials, who said he was executed at his house.

Ali Abdullah Saleh Affash was born on 21 March 1947 to a poor Zaydi family in Beit al-Ahmar village (Red House village) from the Sanhan (سنحان) clan (Sanhan District), whose territories lie some 20 kilometers southeast of Sanaa, then capital of the northern Kingdom of Yemen. Saleh's father, Abdallah Saleh died after he divorced Ali Abdullah's mother when Saleh was still young. His mother later remarried her deceased former husband's brother, Muhammad Saleh, who soon became Saleh's mentor and stepfather. Saleh's brother Mohammed was a major general and had three children: Yahya, Tareq, and Ammar, who all served under Saleh during his rule.

Saleh's cousin, Ali Mohsen al-Ahmar from the Al Ahmar family, which is also part of the Sanhan clan is often confused with the same-named leading family of the Hashid tribe, with which the Sanhan clan was an ally. The Hashid tribe, in turn, belongs to the larger Yemeni parent group, the Kahlan tribe. The clans Sanhan and Khawlan are said to be related.

Ali Abdallah Saleh married Asama Saleh in 1964.

Saleh received his primary education at Ma'alama village before leaving to join the Royal (North Yemeni) Armed Forces in 1958 as an infantry soldier and was admitted to the Royal Military Academy in 1960. Three years later, in 1963, he was commissioned as a second lieutenant in armoured corps. He participated in the Nasserist-inspired military coup of 1962, which was instrumental in the removal of King Muhammad al-Badr and the establishment of the Yemen Arab Republic, beside that he wasn't an Nasserist. During the North Yemen Civil War, he attained the rank of major by 1969. He received further training as a staff officer in the Higher Command and staff C Course in Iraq, between 1970 and 1971, and was promoted to lieutenant colonel. He became a full colonel in 1976 and was given command of a mechanised brigade. In 1977, the President of North Yemen, Ahmad al-Ghashmi, appointed him as military governor of Taiz.