Longest border between two countries

What to remember

Between Canada and the United States, Canada's land border runs for 8,894 km (5,526 mi) in total, of which 8,893 km is shared with its American neighbour. No other pair of countries shares a longer boundary.

The border is not a single line: it is made up of 4 distinct boundaries between the two countries. Canada has only one other land neighbour, Greenland (Denmark), with which it shares a 1.2 km border. In all, the country has 6 distinct land borders with 2 neighbours.

The counting rule matters: borders along lakes, rivers and other internal waters count as land borders. On the other hand, countries connected only by man-made structures such as bridges, causeways or tunnels are not considered to share a land border.