Borders are the boundaries that define a country’s territory and separate it from its neighbors. They can be natural, such as rivers or mountains, or artificial, such as walls or fences. Some countries have small borders, while others have extensive ones. They are established through treaties and other such agreements that delineate boundary lines. These borders are often controlled by the two countries that share it, with border crossings at certain points. Some borders remain points of contention between states who are unable to agree on where the border lies.
Here are the top 20 longest international land borders in the world.
| Rank | Country A | Country B | Border length |
| 1. | Canada | United States | 8,893 km |
| 2. | Kazakhstan | Russia | 7,644 km |
| 3. | Argentina | Chile | 6,691 km |
| 4. | China | Mongolia | 4,630 km |
| 5. | Bangladesh | India | 4,142 km |
| 6. | China | Russia | 4,133 km |
| 7. | Mongolia | Russia | 3,452 km |
| 8. | Bolivia | Brazil | 3,403 km |
| 9. | India | Pakistan | 3,190 km |
| 10. | Mexico | United States | 3,155 km |
| 11. | Afghanistan | Pakistan | 2,670 km |
| 12. | Brazil | Peru | 2,659 km |
| 13. | China | India | 2,659 km |
| 14. | Angola | Democratic Republic of the Congo | 2,646 km |
| 15. | Gabon | Republic of the Congo | 2,567 km |
| 16. | Argentina | Paraguay | 2,531 km |
| 17. | Myanmar | Thailand | 2,416 km |
| 18. | Burma | Thailand | 2,416 km |
| 19. | Colombia | Venezuela | 2,341 km |
| 20. | Democratic Republic of the Congo | Zambia | 2,332 km |
