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. It comprises England, Scotland, Wales and Northern Ireland, with a population of over 69 million in 2024. 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). It shares a land border with the Republic of Ireland and is otherwise surrounded by the Atlantic Ocean, the North Sea, the English Channel, the Celtic Sea and the Irish Sea, while maintaining sovereignty over the British Overseas Territories. The capital and largest city of both England and the UK is London; Edinburgh, Cardiff and Belfast are the national capitals of Scotland, Wales and Northern Ireland.
Britain has been inhabited since the Neolithic. In AD 43 the Roman conquest of Britain began. The Roman departure between 383 and 410 was followed by Anglo-Saxon settlement beginning around 450. In 1066 the Normans conquered England. After the Wars of the Roses, the Kingdom of England began to flourish, resulting in the 16th-century annexation of Wales and the establishment of the British Empire. Over the 17th century the role of the British monarchy was reduced, particularly as a result of the English Civil War. In 1707 the Kingdom of England and the Kingdom of Scotland united under the Treaty of Union to create the Kingdom of Great Britain. In the Georgian era the office of prime minister became established. The Acts of Union 1800 incorporated the Kingdom of Ireland to create the United Kingdom of Great Britain and Ireland in 1801. Most of Ireland seceded from the UK in 1922 as the Irish Free State, and the Royal and Parliamentary Titles Act 1927 created the present United Kingdom.
