The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or UK, is a country located off the northwestern coast of mainland Europe. It consists of four countries: England, Scotland, Wales, and Northern Ireland. The capital city is London, which is also the largest city in the UK. The UK has a rich history and is known for its significant contributions to culture, science, and politics. It operates as a constitutional monarchy with a parliamentary system, where the monarch is the head of state and the Prime Minister is the head of government.