United Kingdom, island country located off the northwestern coast of mainland Europe. The United Kingdom comprises the whole of the island of Great Britain—which contains England, Wales, and Scotland—as well as the northern portion of the island of Ireland. The name Britain is sometimes used to refer to the United Kingdom as a whole. The capital is London, which is among the world’s leading commercial, financial, and cultural centres. Other major cities include Birmingham, Liverpool, and Manchester in England, Belfast and Londonderry in Northern Ireland, Edinburgh and Glasgow in Scotland, and Swansea and Cardiff in Wales.
The United Kingdom comprises four geographic and historical parts—England, Scotland, Wales, and Northern Ireland. The United Kingdom contains most of the area and population of the British Isles—the geographic term for the group of islands that includes Great Britain, Ireland, and many smaller islands. Together England, Wales, and Scotland constitute Great Britain, the larger of the two principal islands, while Northern Ireland and the republic of Ireland constitute the second largest island, Ireland.