The history of the British Isles has witnessed intermittent periods of competition and cooperation between the people that occupy the various parts of Great Britain, Ireland, and the smaller adjacent islands, which together make up the British Isles, as well as with France, Germany, the Low Countries, Denmark, Scandinavia, etc.

Today, the British Isles contain two sovereign states: the Republic of Ireland and the United Kingdom. There are also three Crown dependencies: Guernsey, Jersey and the Isle of Man. The United Kingdom may be further broken down into the four countries of the United Kingdom: England, Northern Ireland, Scotland, and Wales. Each of these countries bears its own history, with all but Northern Ireland having been independent states at one point. The History of the formation of the United Kingdom is very complex.

The British monarch was head of state of all of the countries of the British Isles from the Union of the Crowns in 1603 until the enactment of the Republic of Ireland Act in 1949, although the term "British Isles" was not used in 1603. Additionally, since the independence of Ireland, historians of the region often avoid the term British Isles due to the complexity of relations between the peoples of the archipelago (see: Terminology of the British Isles).