In simple words, A boundary line is a line along which two areas meet. Boundary Lines are established through agreements between political or social entities that control those areas; the creation of these agreements is called boundary delimitation. Many of the noted boundary lines of the world are based on latitude or longitude serving as the boundary line. The most notable ones are the 49th parallel (49 degrees North Latitude) that divides USA (excluding Alaska) and Canada, and 38th Parallel (38 degrees North Latitude) that divides North Korea and South Korea etc. In this article, we shall see a list of important boundary lines of the world.
List of Important Boundary Lines of the World
| Name of Boundaries / Lines | Between | Description |
| 17th Parallel | South Vietnam and North Vietnam | It is the 17 degrees North latitude divided erstwhile North and South Vietnam. It was demarcated based on the 1954 Geneva Accords. The 17th parallel became irrelevant after the unification of Vietnam in 1976. |
| 20th Parallel | Libya and Sudan | It is the 20 degrees north latitude which is used as the border between Sudan and Libya. |
| 22nd Parallel | Egypt and Sudan | The 22nd latitude north of the equator marks a major portion of the Sudan-Egypt border. |
| 25th Parallel | Mauritania and Mali | The northernmost section of the Mali-Mauritania border is marked using this line. |
| 31st Parallel | Iran and Iraq | The 31st northern latitude marks the border between Iraq and Iran. It also demarcates the border between the USA states of Louisiana and Mississippi. |
| 38th Parallel | South Korea and North Korea | The 38th parallel is used to demarcate the central part of the Demilitarized zone between North and South Korea. |
| 49th Parallel | The USA and Canada | It is located on the 49 degrees north latitude of the equator. It serves as the international border between the northern USA (Excluding Alaska) and Canada. It is demarcated after the Anglo-American Convention of 1818 and the Oregon Treaty of 1846. |
| Blue Line | Lebanon and Israel | A border demarcation between Lebanon and Israel published by the United Nations on 7 June 2000 for the purposes of determining whether Israel had fully withdrawn from Lebanon. |
| Durand Line | Pakistan and Afghanistan | Serves as boundary line between Pakistan and Afghanistan. This boundary line was demarcated by Sir Mortimer Durand in 1893. Present-day Afghanistan does not recognize the Durand line. |
| Green Line / Attila Line / UN Buffer Zone | The Republic of Cyprus and Turkish Cyprus | This is a demilitarized zone. It was established in 1964 and extended in 1974 after the ceasefire of 16 August 1974. It is patrolled by the United Nations Peacekeeping Force in Cyprus (UNFICYP). |
| Hindenburg Line | Poland and Germany | It was a German Defensive line in French territory during World War I. It became irrelevant after the treaty of Versailles in 1919. |
| Maginot Line | Germany and France | It was a defensive line of fortifications, weapon installations, and obstacles built by the French in the 1930’s before World War II along the German – French Border to deter any invasion by Germany. It became obsolete following the successful invasion of France by Germany during World War II. |
| Mannerheim Line | Russia and Finland | This is a defensive line built by Finland against the Soviet Union for the Winter War during World War II. |
| McMahon Line | China and India | It is the current de facto border between India and China. It was demarcated by Sir Henry McMahon in consultation with Tibetan representatives in 1914. China disputes the legal status of this line. |
| Oder-Neisse Line | Poland and Germany | It runs along the rivers Oder and Lusatian Neisse rivers. It demarcates the Polish-German border according to the Potsdam Conference. |
| Radcliffe Line | India and Pakistan | It demarcated the Punjab and Bengal provinces of the British India between India and Pakistan. It was demarcated by Sir Cyril Radcliffe. Today if forms the border between India and Pakistan, and India and Bangladesh. |
| Siegfried Line | France and Germany | It was built as an extension of the Hindenburg defensive line on the western front of World War I by the Weimar Republic and later the Third Reich of Germany in the 1930s. |