Blue Line (Lebanon) in the context of "United Nations Security Council Resolution 426"

The Israeli occupation of Southern Lebanon lasted for eighteen years, from 1982 until 2000. In June 1982, Israel invaded Lebanon in response to attacks from southern Lebanon by Palestinian militants. The Israel Defense Forces (IDF) occupied the southern half of Lebanon as far as the capital city Beirut, together with allied Maronite Christian paramilitaries involved in the Lebanese Civil War. The IDF left Beirut on 29 September 1982, but continued to occupy the country's southern half. Amid rising casualties from guerrilla attacks, the IDF withdrew south to the Awali river on 3 September 1983.

From February to April 1985, the IDF carried out a phased withdrawal to a "Security Zone" along the border, which it said was to protect northern Israel. From this point onwards, Israel supported the South Lebanon Army (SLA), the Lebanese Christian paramilitary, against Hezbollah and other Muslim militants. They fought a guerrilla war in Southern Lebanon throughout the occupation.

The United Nations Interim Force in Lebanon (Arabic: قوة الأمم المتحدة المؤقتة في لبنان; Hebrew: כוח האו"ם הזמני בלבנון), or UNIFIL (Arabic: يونيفيل; Hebrew: יוניפי״ל) is a United Nations peacekeeping mission established on 19 March 1978 by United Nations Security Council Resolutions 425 and 426, and several further resolutions in 2006 to confirm Hezbollah demilitarisation, support Lebanese army operations against insurgents and weapon smuggling, and confirming Israeli withdrawal from Lebanon, in order to ensure that the government of Lebanon would restore its effective authority in the area. The 1978 South Lebanon conflict came in the context of Palestinian insurgency in South Lebanon and the Lebanese Civil War.

The mandate had to be adjusted due to the Israeli invasion of Lebanon in 1982 and after the Israeli withdrawal from Lebanon in 2000. Following the 2006 Lebanon War, the United Nations Security Council enhanced UNIFIL and added additional tasks to the mandate such as aiding displaced persons.

The 1978 South Lebanon conflict, also known as the First Israeli invasion of Lebanon and codenamed Operation Litani by Israel, began when Israel invaded southern Lebanon up to the Litani River in March 1978. It was in response to the Coastal Road massacre near Tel Aviv by Palestinian militants based in Lebanon. The conflict resulted in the deaths of 1,100–2,000 Lebanese and Palestinians, 20 Israelis, and the internal displacement of 100,000 to 250,000 people in Lebanon. The Israel Defense Forces gained a military victory against the Palestine Liberation Organization (PLO) as the latter was forced to withdraw from southern Lebanon, preventing it from launching attacks on Israel from across its land border with Lebanon. In response to the outbreak of hostilities, the United Nations Security Council adopted Resolution 425 and Resolution 426 on 19 March 1978, which called on Israel to immediately withdraw its troops from Lebanon and established the United Nations Interim Force in Lebanon (UNIFIL).

Israel launched a second invasion of Lebanon in 1982.

Israel–Lebanon relations have experienced ups and downs since their establishment in the 1940s.

Lebanon did take part in the 1948 Arab–Israeli War against Israel, but Lebanon was the first Arab League nation to signal a desire for an armistice treaty with Israel in 1949. Lebanon did not participate in the Six-Day War in 1967, nor the Yom Kippur War in 1973 in any significant way, and until the early 1970s, Lebanon's border with Israel was the calmest frontier between Israel and any of the other adjacent Arab League states.