The longest border between any two countries in the world is between:

The correct answer is Option 1.

Key Points

1. Canada and the United States of America:

   • Border Length: The Canada–United States border is the longest international border in the world, stretching approximately 8,891 kilometers (5,525 miles). Hence option 1 is correct
   • Characteristics:
     • It is the longest undefended border globally, marked by cooperation and mutual trust between the two countries.
     • The border spans diverse geographical features, including rivers, lakes, forests, and mountain ranges, with various border crossings facilitating significant trade and travel.

2. Chile and Argentina:

   • Border Length: The Chile–Argentina border is one of the longest borders in the world, stretching approximately 5,308 kilometers (3,300 miles).
   • Characteristics:
     • It traverses the rugged terrain of the Andes mountains, making it one of the most challenging international borders to traverse.
     • The border regions are known for their natural beauty, including national parks and reserves on both sides, attracting tourists and adventurers.

3. China and India:

   • Border Length: The China–India border stretches over approximately 3,488 kilometers (2,167 miles).
   • Characteristics:
     • This border is one of the most complex and disputed borders globally, with differing interpretations of the Line of Actual Control (LAC).
     • The region includes high-altitude areas in the Himalayas, with harsh climatic conditions and occasional border tensions between the two nations.

4. Kazakhstan and Russian Federation:

   • Border Length: The Kazakhstan–Russia border is approximately 7,644 kilometers (4,750 miles) long.
   • Characteristics:
     • It is the longest continuous land border between two countries, traversing vast steppes, deserts, and mountainous regions.
     • The border has historical significance, reflecting the shared cultural, economic, and political ties between Kazakhstan and Russia.

• Hence, Canada and the United States of America, with their approximately 8,891 kilometers (5,525 miles) long border being the longest international border globally.