The United Nations Buffer Zone in Cyprus is a demilitarized zone, patrolled by the United Nations Peacekeeping Force in Cyprus (UNFICYP), that was established on 4 March 1964. It was extended on 9 August after the Battle of Tillyria and extended again in 1974 after the ceasefire of 16 August 1974, following the Turkish invasion of Cyprus and the de facto partition of the island into the area controlled by the Republic of Cyprus (excluding the British Sovereign Base Areas) and the largely unrecognized Turkish Republic of Northern Cyprus in the north. The zone, also known as the Green Line (Greek: Πράσινη Γραμμή, Prasini Grammi; Turkish: Yeşil Hat), stretches for 180 kilometres (112 miles) from Paralimni in the east to Kato Pyrgos in the west, where a separate section surrounds Kokkina.

The dividing line is also referred to as the Attila Line, named after Turkey's 1974 military invasion, codenamed Operation Attila. The Turkish army has built a barrier on the zone's northern side, consisting mainly of barbed-wire fencing, concrete wall segments, watchtowers, anti-tank ditches, and minefields. The zone cuts through the centre of Nicosia, separating the city into southern and northern sections. In total, it spans an area of 346 square kilometres (134 sq mi), varying in width from less than 20 metres (66 ft) to more than 7 kilometres (4.3 mi). After the fall of the Berlin Wall in 1989, Nicosia remains the last divided capital in Europe. Some 10,000 people live in several villages and work on farms located within the zone; the village of Pyla is famous for being one of the few remaining villages in Cyprus where Greek and Turkish Cypriots still live side by side. Other villages are Deneia, Athienou, and Troulloi. Some areas are untouched by human interference and have remained a safe haven for flora and fauna.

A buffer zone in Cyprus was first established in the last days of 1963, when Major-General Peter Young was the commander of the British Joint Force (later known as the Truce Force and a predecessor of the present UN force). This Force was set up in the wake of the intercommunal violence of Christmas 1963. On 30 December 1963, following a 'high powered' twelve hour meeting chaired by Duncan Sandys (British Secretary of State for Commonwealth Relations), General Young drew the agreed cease-fire line on a map with a green chinagraph pencil, which was to become known as the "Green Line". Brigadier Patrick Thursby also assisted in devising and establishing the Green Line.

This map was then passed to General Young's intelligence officer, who was waiting in a nearby building and told to "Get on with it." Intelligence Corps NCOs then copied the map for distribution to the Truce Force units. Further copies of the map would then have been produced 'in house' for use by Truce Force patrols.

The Green Line became impassable following the July 1974 Turkish invasion of Cyprus during which Turkey occupied approximately 37% of Cypriot territory, in response to a short-lived Greek Cypriot coup. A "security zone" was established after the Tripartite Conference of Geneva in July 1974. Pursuant to United Nations Security Council Resolution 353 of 1974, the foreign ministers of Greece, Turkey, and the United Kingdom convened in Geneva on 25 July 1974. According to UNFICYP, the text of the joint declaration transmitted to the Secretary-General of the United Nations was as follows:

A security zone of a size to be determined by representatives of Greece, Turkey, and the United Kingdom, in consultation with UNFICYP, was to be established at the limit of the areas occupied by the Turkish armed forces. This zone was to be entered by no forces other than those of UNFICYP, which was to supervise the prohibition of entry. Pending the determination of the size and character of the security zone, the existing area between the two forces was not to be breached by any forces.

— Tripartite Conference & Geneva Declaration,

The UN Security Council then adopted the above declaration with Resolution 355. When the coup dissolved, the Turkish Armed Forces advanced to capture approximately 37% of the island and met the "Green Line". The meandering Buffer Zone marks the southernmost points that the Turkish troops occupied during the Turkish Invasion of Cyprus in August 1974, running between the ceasefire lines of the Cypriot National Guard and Turkish army that de facto divides Cyprus into two, cutting through the capital of Nicosia. With the self-proclamation of the internationally unrecognized "Turkish Republic of Northern Cyprus", the Buffer Zone became its de facto southern border.^{[citation needed]}