The Sabra and Shatila massacre was the killing in Lebanon of between 460 and 3,500 civilians—mostly Palestinians and Lebanese Shiites—by the militia of the Lebanese Forces. The group was a Maronite Christian Lebanese right-wing party under the command of Elie Hobeika. It committed the atrocity in the Sabra neighborhood and the adjacent Shatila refugee camp, in Beirut. President Bachir Gemayel had been assassinated two days earlier and the Phalangists sought revenge.

From approximately 18:00 on 16 September to 08:00 on 18 September 1982, a widespread massacre was carried out by the militia, while the Israeli Defence Forces (IDF) had the camp surrounded. The militia had been ordered by the IDF to clear Palestine Liberation Organization (PLO) fighters out of Sabra and Shatila, as part of the IDF's maneuvering into West Beirut. As the massacre unfolded, the IDF received reports of atrocities but did not take any action to prevent or stop the massacre.

In June 1982, the IDF had invaded Lebanon with the intention of rooting out the PLO. By 30 August 1982, under the supervision of the Multinational Force, the PLO withdrew from Lebanon following weeks of battles in West Beirut and shortly before the massacre took place. Various forces — Israeli, Lebanese Forces and possibly also the South Lebanon Army (SLA) — were in the vicinity of Sabra and Shatila at the time of the slaughter, taking advantage of the fact that the Multinational Force had removed barracks and mines that had encircled Beirut's predominantly Muslim neighborhoods and kept the Israelis at bay during the Beirut siege. The Israeli advance over West Beirut in the wake of the PLO withdrawal, which enabled the Lebanese Forces raid, was in violation of the ceasefire agreement between the various forces. The Israeli Army surrounded Sabra and Shatila and stationed troops at the exits of the area to prevent camp residents from leaving and, at the request of the Lebanese Forces, fired illuminating flares at night.

According to Alain Menargues, the direct perpetrators of the killings were the "Young Men", a gang recruited by Elie Hobeika (the Lebanese Forces intelligence chief and liaison officer with Mossad), from men who had been expelled from the Lebanese Forces for insubordination or criminal activities. The killings are widely believed to have taken place under Hobeika's direct orders. Hobeika's family and fiancée had been murdered by Palestinian militiamen and their Lebanese allies during the 1976 Damour massacre, itself a response to the Karantina massacre of Palestinians and Lebanese Muslims at the hands of Christian militants two days before. In all 300–400 militiamen were involved, including some from Sa'ad Haddad's South Lebanon Army.

In February 1983, a commission chaired by Seán MacBride, the assistant to the UN Secretary General and President of United Nations General Assembly at the time, looking into reported violations of International Law by Israel concluded that Israel, as the camp's occupying power, bore responsibility for the violence. The commission also concluded that the massacre was a form of genocide.

In February 1983, the Israeli Kahan Commission, appointed to investigate the incident, found that Israeli military personnel, aware that a massacre was in progress, had failed to take serious steps to stop it. The commission deemed Israel indirectly responsible, and Ariel Sharon, then Defense Minister, bore personal responsibility "for ignoring the danger of bloodshed and revenge", forcing him to resign.