Longest Land Border between two Countries in the World

The longest land Border between two states in the World is the Canada–United States border officially known as the International Boundary. The borderland is shared between Canada and the United States that are the second- and fourth-largest countries in the world by area, respectively. 

The earthly boundary (including portions of Marines in the Great Lakes, and in the Atlantic, Pacific, and Arctic coasts) is 8,891 kilometres (5,525 mi) long out of which two-eight of the Border i.e. 2,475 kilometres (1,538 mi) is shared between Canada and US’s largest state Alaska. The Border is shared between eight Canadian provinces and territories (Yukon, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, and New Brunswick), and thirteen U.S. states (Alaska, Washington, Idaho, Montana, North Dakota, Minnesota, Michigan, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine).