| Boundary Line | Separates | Important Facts / Exam Points |
| Maginot Line | France – Germany | Fortification built by France after World War I; bypassed by Germany during World War II. |
| Mannerheim Line | Finland – Russia | Finnish defensive line against the Soviet Union during the Winter War (1939–40). |
| McMahon Line | India – China | Drawn in 1914 at the Shimla Convention; China does not recognize it. Forms most of Arunachal Pradesh’s boundary with Tibet (China). |
| Durand Line | Pakistan – Afghanistan | Drawn in 1893 by Sir Mortimer Durand; Afghanistan has never officially accepted it as a permanent international border. |
| Radcliffe Line | India – Pakistan | Drawn by Sir Cyril Radcliffe in 1947 during the Partition of India. |
| 38th Parallel | North Korea – South Korea | Approximate division of the Korean Peninsula after World War II. The DMZ lies close to this line. |
| 49th Parallel | United States – Canada | Forms most of the international boundary between the USA and Canada. |
| Hindenburg Line | Germany (WWI defensive line) | Not an international boundary; a German defensive line during World War I. Often confused as a boundary line in older GK books. |
| Line of Control (LoC) | India – Pakistan (Jammu & Kashmir) | Military control line established after the 1972 Simla Agreement; not an international boundary. |
| Line of Actual Control (LAC) | India – China | De facto border between India and China; not mutually agreed upon. |
| International Border (IB) | India – Pakistan | Officially recognized international boundary (except Jammu & Kashmir). |
| Siegfried Line | Germany – France | German defensive fortification opposite the French Maginot Line. |
| Oder–Neisse Line | Germany – Poland | Established after World War II; present international boundary. |
| Green Line | Israel and the West Bank / Gaza | Armistice line established after the 1948 Arab–Israeli War. |
| Blue Line | Israel – Lebanon | Boundary identified by the United Nations in 2000. |
| Purple Line | Israel – Syria (Golan Heights) | Ceasefire line after the 1967 Six-Day War. |
| 17th Parallel | North Vietnam – South Vietnam (historical) | Temporary military demarcation established by the Geneva Accords (1954). |
| 22nd Parallel | Egypt – Sudan | International boundary; includes the disputed Hala’ib Triangle. |
