Which countries share the longest border?

The United States and Canada don't only share the longest border in the world. They share a border that runs approximately 5,525 miles (8,891 kilometers) from the Atlantic to the Pacific Ocean plus another 1,538 miles (2,475 kilometers) between Canada and Alaska.

This is what makes the border between the US and Canada not just the world’s longest international boundary between two countries, but also the world’s longest demilitarized border – for the most part, it’s lightly patrolled and relics a relatively free flow of people entering and leaving the neighbouring countries at regularly designated entry points.