The Suez Crisis, or the Second Arab–Israeli war, also called the Tripartite Aggression (Arabic: العدوان الثلاثي, romanized: Al-ʿUdwān aṯ-Ṯulāṯiyy) in the Arab world and the Sinai War in Israel, was an invasion of Egypt in late 1956 by Israel, followed by the United Kingdom and France. The aims were to regain control of the Suez Canal for the Western powers and to remove Egyptian president Gamal Abdel Nasser, who had just swiftly nationalised the foreign-owned Suez Canal Company, which administered the canal. Israel's primary objective was to re-open the blocked Straits of Tiran. After the fighting had started, political pressure from the United States, the Soviet Union, and the United Nations led to a withdrawal by the three invaders. The episode humiliated the United Kingdom and France and strengthened Nasser.

On 26 July 1956, Nasser nationalised the Suez Canal Company, which prior to that was owned primarily by British and French shareholders. On 29 October, Israel invaded the Egyptian Sinai. Britain and France issued a joint ultimatum to cease fire, which was ignored. On 5 November, Britain and France landed paratroopers along the Suez Canal. Before the Egyptian forces were defeated, they had blocked the canal to all shipping by sinking 40 ships in the canal. It later became clear that Israel, France and Britain had conspired to plan the invasion. The three allies had attained a number of their military objectives, but the canal was useless. Heavy political pressure from the United States and the USSR led to a withdrawal. U.S. president Dwight D. Eisenhower had strongly warned Britain not to invade; he threatened serious damage to the British financial system by selling the U.S. government's pound sterling bonds. Historians conclude the crisis "signified the end of Great Britain's role as one of the world's major powers".

The Suez Canal was closed from October 1956 until March 1957. Israel fulfilled some of its objectives, such as attaining freedom of navigation through the Straits of Tiran, which Egypt had blocked to Israeli shipping since 1948–1950.

As a result of the conflict, the United Nations created the UNEF Peacekeepers to police the Egyptian–Israeli border, British prime minister Anthony Eden resigned, Canadian external affairs minister Lester Pearson won the Nobel Peace Prize, and the USSR may have been emboldened to invade Hungary.