The history of the United Kingdom as a unified sovereign state began in 1707 with the political union of the kingdoms of England and Scotland into a united kingdom called Great Britain. Of this new state the historian Simon Schama said "What began as a hostile merger would end in a full partnership in the most powerful going concern in the world... it was one of the most astonishing transformations in European history." A further Act of Union in 1800 added the Kingdom of Ireland to create the United Kingdom of Great Britain and Ireland.

The first decades were marked by Jacobite risings which ended with defeat for the Stuart cause at Culloden in 1746. In 1763 victory in the Seven Years War led to the dominance of the British Empire which was to be the foremost global power for over a century and grew to become the largest empire in history. As a result the culture of the United Kingdom and its industrial political constitutional educational and linguistic influence became worldwide.

In 1922 following the Anglo-Irish Treaty most of Ireland seceded to become the Irish Free State; a day later Northern Ireland seceded from the Free State and returned to the United Kingdom. As a result in 1927 the United Kingdom changed its formal title to the "United Kingdom of Great Britain and Northern Ireland" usually shortened to "Britain" and (after 1945) to the "United Kingdom" or "UK".