Ali Abdullah Saleh Affash (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.