Which country has the world's longest official name?

The United Kingdom has the world’s longest official country name: the United Kingdom of Great Britain and Northern Ireland.

The name reflects the state’s constitutional history. “Great Britain” means the island containing England, Scotland and Wales, while “Northern Ireland” identifies the part of Ireland included in the United Kingdom. The full title dates from 1927, after the Irish Free State became independent and Northern Ireland remained within the UK.

The country is commonly called the United Kingdom or the UK, and Great Britain is often used informally—but the terms are not identical. Great Britain excludes Northern Ireland, while the United Kingdom includes England, Scotland, Wales and Northern Ireland. England is only one constituent country of the UK, not a synonym for the whole state.

The UK’s long official title is also why it frequently tops trivia lists about country names. It is a formal state title used in legal and diplomatic contexts, rather than the short name people normally use in conversation.