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

The border between Canada and the United States is the longest international border in the world, stretching approximately 8,891 kilometers (5,525 miles), including the border shared with Alaska. It is a peaceful boundary and includes both land and water segments. Chile and Argentina: * Length: Approx. 5,308 kilometres * This is the third-longest international border in the world and the longest in South America. * It follows the Andes mountain range for most of its length, with several high-altitude border crossings. China and India: * Length: Approx. 3,488 kilometers
* It is highly disputed in areas such as Aksai Chin and Arunachal Pradesh, leading to occasional tensions between the two nations. Kazakhstan and Russian Federation: * Length: Approx. 7,644 kilometers * This is the second-longest international border in the world. * It is largely flat, passing through vast steppes, and is a vital region for trade and natural resources between the two countries.