The 1948 (or First) Arab–Israeli War was the second and final stage of the 1947–1949 Palestine war. It formally began following the end of the British Mandate for Palestine at midnight on 14 May 1948; the Israeli Declaration of Independence had been issued earlier that day, and a military coalition of Arab states entered the territory of British Palestine in the morning of 15 May.

The first deaths of the 1947–1949 Palestine war occurred on 30 November 1947 during an ambush of two buses carrying Jews. There had been tension and conflict between the Arabs and the Jews, and between each of them and the British forces since the 1917 Balfour Declaration and the 1920 creation of the British Mandate of Palestine. British policies dissatisfied both Arabs and Jews. Arab opposition developed into the 1936–1939 Arab revolt in Palestine, while the Jewish opposition developed into the 1944–1947 Jewish insurgency in Palestine. In 1947, these ongoing tensions erupted into civil war following the 29 November 1947 adoption of the United Nations Partition Plan for Palestine, which planned to divide Palestine into an Arab state, a Jewish state, and the Special International Regime encompassing the cities of Jerusalem and Bethlehem.

On 15 May 1948, the civil war transformed into a conflict between Israel and the Arab states following the Israeli Declaration of Independence the previous day. Egypt, Transjordan, Syria, and expeditionary forces from Iraq entered Palestine. The invading forces took control of the Arab areas and immediately attacked Israeli forces and several Jewish settlements. The 10 months of fighting took place mostly on the territory of the British Mandate and in the Sinai Peninsula and southern Lebanon, interrupted by several truce periods.As a result of the war, the State of Israel controlled the area that the UN had proposed for the Jewish state, as well as almost 60% of the area proposed for the Arab state, including the Jaffa, Lydda, and Ramle area, Galilee, some parts of the Negev, a wide strip along the Tel Aviv–Jerusalem road, and some territories in the West Bank. Israel also took control of West Jerusalem, which was meant to be part of an international zone for Jerusalem and its environs. Transjordan took control of East Jerusalem and the remainder of the former British mandate, annexing it the following year, and the Egyptian military took control of the Gaza Strip. At the Jericho Conference on 1 December 1948, 2,000 Palestinian delegates called for unification of Palestine and Transjordan as a step toward full Arab unity. The conflict triggered significant demographic change throughout the Middle East. Around 700,000 Palestinian Arabs fled or were expelled from their homes in the area that became Israel, and they became Palestinian refugees in what they refer to as the Nakba ("the catastrophe"). In the three years following the war, about 700,000 Jews emigrated to Israel. Around 260,000 Jews moved to Israel from the Arab world during and immediately after the war.