The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK, or Britain,is a sovereign island country located off the northwestern coast of mainland Europe. The UK consists of four countries: England, Scotland, Wales and Northern Ireland.The United Kingdom is a constitutional monarchy with Her Majesty Queen Elizabeth II of the United Kingdom of Great Britain and Northern Ireland, as head of state; the monarch of the UK serves as head of state of fifteen other Commonwealth countries, putting the UK in a personal union with those other states.