The North Yemen Civil War (Arabic: ثورة 26 سبتمبر, romanized: Thawra 26 Sabtambar, lit. '26 September Revolution') was fought in North Yemen from 1962 to 1970 between partisans of the Mutawakkilite Kingdom and supporters of the Yemen Arab Republic. The war began with a coup d'état carried out in 1962 by revolutionary republicans led by the army under the command of Abdullah as-Sallal, who dethroned the newly crowned Imam Muhammad al-Badr and declared Yemen a republic under his presidency. The Imam escaped to the Saudi Arabian border where he rallied popular support from northern Shia tribes to retake power, escalating rapidly to a full-scale civil war.

On the royalist side, Jordan, Saudi Arabia and Israel supplied military aid, and Britain gave covert support, while the republicans were supported by Egypt (then formally known as the United Arab Republic) and were supplied warplanes from the Soviet Union. Both foreign irregular and conventional forces were involved. Egyptian President Gamal Abdel Nasser supported the republicans with as many as 70,000 Egyptian troops and weapons. Despite several military actions and peace conferences, the war sank into a stalemate by the mid-1960s.

Egypt's commitment to the war is considered to have been detrimental to its performance in the Six-Day War of June 1967, after which Nasser found it increasingly difficult to maintain his army's involvement and began to pull his forces out of Yemen. The surprising removal of Sallal on November 5 by Yemeni dissidents, supported by republican tribesmen, resulted in an internal shift of power in the capital, while the royalists approached it from the north. The new republic government was headed by Qadi Abdul Rahman Iryani, Ahmed Noman and Mohamed Ali Uthman, all of whom shortly either resigned or fled the country, leaving the disarrayed capital under the control of Prime Minister Hassan al-Amri. The 1967 siege of Sana'a became the turning point of the war. The remaining republican Prime Minister succeeded in keeping control of Sana'a and by February 1968, the royalists lifted the siege. Clashes continued in parallel with peace talks until 1970, when Saudi Arabia recognized the Republic, and a ceasefire came into effect.Egyptian military historians refer to the war in Yemen as "their Vietnam." Historian Michael Oren (former Israeli Ambassador to the U.S) wrote that Egypt's military adventure in Yemen was so disastrous that "the imminent Vietnam War could easily have been dubbed 'America's Yemen.'"