The United Nations Truce Supervision Organization (UNTSO) is an organization founded on 29 May 1948  by the Security Council in resolution 50 (1948) for peacekeeping in the Middle East.

Its primary task was providing the military command structure to the peace keeping forces in the Middle East to enable the peace keepers to observe and maintain the cease-fire, and as may be necessary in assisting the parties to the Armistice Agreements in the supervision of the application and observance of the terms of those Agreements.

Following the wars of 1956, 1967 and 1973, the functions of the observers changed in the light of changing circumstances, but they remained in the area, acting as go-betweens for the hostile parties and as the means by which isolated incidents could be contained and prevented from escalating into major conflicts. 

UNTSO personnel have also been available at short notice to form the nucleus of other peacekeeping operations on a temporary basis. The ability of UNTSO military observers to deploy after the Security Council acted to establish a new operation has been an important factor contributing to the initial effectiveness of such missions. 

In the Middle East, groups of UNTSO military observers are today attached to the peacekeeping forces in the area: the United Nations Disengagement Observer Force (UNDOF) on the Golan and the United Nations Interim Force in Lebanon (UNIFIL). In addition, UNTSO maintains liaison offices in Egypt, Lebanon, Syria, and Jerusalem for liaison with Israel and Jordan.