The Six-Day War (Hebrew: מִלְחֶמֶת שֵׁשֶׁת הַיָּמִים, Milḥemet Šešet HaYamim; Arabic: النكسة, an-Naksah, lit. 'The Setback' or حرب 1967, Ḥarb 1967, 'War of 1967') or June War, also known as the 1967 Arab–Israeli War or Third Arab–Israeli War, was fought between Israel and a coalition of Arab states (primarily Egypt, Syria, and Jordan) from 5 to 10 June 1967.

Escalated hostilities broke out amid poor relations between Israel and its Arab neighbours following the 1949 Armistice Agreements, which were signed at the end of the First Arab–Israeli War. Earlier, in 1956, regional tensions over the Straits of Tiran escalated in what became known as the Suez Crisis, when Israel invaded Egypt over the Egyptian closure of maritime passageways to Israeli shipping, ultimately resulting in the re-opening of the Straits of Tiran to Israel as well as the deployment of the United Nations Emergency Force (UNEF) along the Egypt–Israel border. In the months prior to the outbreak of the Six-Day War in June 1967, tensions again became dangerously heightened: Israel reiterated its post-1956 position that another Egyptian closure of the Straits of Tiran to Israeli shipping would be a definite casus belli. In May 1967, Egyptian president Gamal Abdel Nasser announced that the Straits of Tiran would again be closed to Israeli vessels. He subsequently mobilized the Egyptian military along the border with Israel, and also ordered the immediate withdrawal of all UNEF personnel.

On 5 June 1967, as the UNEF was in the process of leaving the zone, Israel launched a series of pre-emptive airstrikes against Egyptian airfields and other facilities, launching its war effort. Egyptian forces were caught by surprise, and nearly the entirety of Egypt's military aerial assets were destroyed, giving Israel the advantage of air supremacy. Simultaneously, the Israeli military launched a ground offensive into Egypt's Sinai Peninsula as well as the Egyptian-occupied Gaza Strip. After some initial resistance, Nasser ordered an evacuation of the Sinai Peninsula; by the sixth day of the conflict, Israel had occupied the entire Sinai Peninsula. Jordan, which had entered into a defense pact with Egypt just a week before the war began, did not take on an all-out offensive role against Israel. However, the Jordanians did launch attacks against Israeli forces to slow Israel's advance. On the fifth day, Syria joined the war by shelling Israeli positions in the north.

Egypt and Jordan agreed to a ceasefire on 8 June, and Syria on 9 June, and it was signed with Israel on 11 June. The Six-Day War resulted in more than 20,000 Arab casualties, with Israeli losses standing at fewer than 1,000 casualties. Alongside the combatant casualties were the deaths of 20 Israeli civilian killed in Arab forces air strikes on Jerusalem, 15 UN peacekeepers killed by Israeli strikes in the Sinai at the outset of the war, and 34 US personnel killed in the USS Liberty incident in which Israeli air forces struck a United States Navy technical research ship.

At the time of the cessation of hostilities, Israel had seized Syria's Golan Heights, the Jordanian-annexed West Bank (including East Jerusalem), and Egypt's Sinai Peninsula as well as the Egyptian-occupied Gaza Strip. The displacement of civilian populations as a result of the Six-Day War would have long-term consequences, as around 280,000 to 325,000 Palestinians and 100,000 Syrians fled or were expelled from the West Bank and the Golan Heights, respectively. Nasser resigned in shame following Israel's victory, but was later reinstated following a series of protests across Egypt. In the aftermath of the conflict, Egypt closed the Suez Canal until 1975, providing a trigger for the 1970s energy crisis and 1973 oil crisis due to the impact on oil deliveries coming from the Middle East to Europe through the Suez Canal.