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.

UNIFIL's mandate is renewed annually by the United Nations Security Council; it was most recently extended on 28 August 2024 with the passing of United Nations Security Council Resolution 2749. It is composed of 10,000 peacekeepers from 46 nations, tasked with helping the Lebanese Army keep the south of the country protected from "unauthorized armed personnel, such as Hezbollah". Its funding is approved on an annual basis by the General Assembly. It had a budget of $474 million for the period July 2018 to June 2019.

According to its Mandate, established by United Nations Security Council Resolutions 425 and 426 in 1978, UNIFIL is tasked with the following objectives:

In addition, several further Security Council resolutions have reaffirmed and expanded the mission's mandate, including:

Under SC Resolution 1701, UNIFIL's mandate was expanded, giving it new duties:

In addition, UNIFIL was also authorized to:

take all necessary action in areas of deployment of its forces and as it deems within its capabilities, to ensure that its area of operations is not utilized for hostile activities of any kind, to resist attempts by forceful means to prevent it from discharging its duties under the mandate of the Security Council, and to protect United Nations personnel, facilities, installations and equipment, ensure the security and freedom of movement of United Nations personnel, humanitarian workers and, without prejudice to the responsibility of the Government of Lebanon, to protect civilians under imminent threat of physical violence.