| Wallace Line | Asia – Australia (Indonesia region) | Invisible line splitting Asian & Australian fauna | Biogeographical |
| 38th Parallel | North Korea – South Korea | Divides Korean Peninsula into two countries | Political |
| Nine-Dash Line | South China Sea | U-shaped line used by China to claim ~90% of the sea (disputed islands & waters) | Maritime / Political |
| Mason–Dixon Line | Pennsylvania, Maryland, Delaware (USA) | Historic boundary; symbol of North vs South USA division | Historical |
| Sykes–Picot Line / Agreement (1916) | Middle East (Ottoman Empire region) | Secret pact between Britain & France (with Russian approval) to divide Arab territories | Historical / Political |
| Hindenburg Line | Germany (Western Front, WW-I) | German defensive line during World War I | Military |
| Green Line (Israel–Palestine) | Israel – Palestine | Armistice line; basis of territorial disputes | Political |
| Green Line (Cyprus) | Cyprus | Divides Greek Cypriot & Turkish Cypriot regions | Political |
| Maginot Line | France–Germany border | France’s defensive line; failed in WWII | Military |
| Siegfried Line (Westwall) | Germany (Western border) | German defensive system (~630 km from Cleve to Switzerland) built in 1930s | Military |