大不列颠及北爱尔兰联合王国（英语：United Kingdom of Great Britain and Northern Ireland），简称联合王国（英语：United Kingdom；UK）或不列颠（英语：Britain）中文通称英国是欧洲的一个主权国家，位于欧洲大陆西北面，由大不列颠岛（英语：Great Britain，亦为该国通称之一）、爱尔兰岛东北部分及一系列较小岛屿共同组成英国同另一国家唯一的陆上国境线位于北爱尔兰，同爱尔兰共和国相邻。英国由大西洋所环绕，东为北海，南为英吉利海峡，西南偏南为凯尔特海，同爱尔兰隔爱尔兰海相望。该国总面积达93,800平方英里（243,000平方公里），为世界面积第80大的主权国家及欧洲面积第11大的主权国家，人口达6450万，为全球第22名。

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a sovereign state in Europe. Lying off the north-western coast of the European mainland, it includes the island of Great Britain (the name of which is also loosely applied to the whole country), the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the UK that shares a land border with another state—the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, with the North Sea to its east, the English Channel to its south and the Celtic Sea to its south-southwest. The Irish Sea lies between Great Britain and Ireland. With an area of 93,800 square miles (243,000 km), the UK is the 80th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 64.5 million inhabitants.