The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of the continental mainland.

The UK includes the island of Great Britain, the north-eastern part of the island of Ireland, and most of the smaller islands within the British Isles, covering 94,354 square miles (244,376 km). Northern Ireland shares a land border with the Republic of Ireland; otherwise, the United Kingdom is surrounded by the Atlantic Ocean, the North Sea, the English Channel, the Celtic Sea, and the Irish Sea. The United Kingdom had an estimated population of 68.2 million people. The capital and largest city of both England and the United Kingdom is London, whose wider metropolitan area is the largest 

in Western Europe, with a population of 14.9 million. The cities of Edinburgh, Cardiff, and Belfast are the national capitals of Scotland, Wales, and Northern Ireland, respectively.