The Acts of Union were twin Acts of Parliament passed in 1707 (going into effect on 26 March) in the Scottish and the English Parliaments. The effect was twofold:
  • to create a new Kingdom of Great Britain (though the name was used on occasion since 1604 to refer to the separate Kingdoms of England and Scotland, which since 1603 had a shared monarch, when speaking of the kingdoms together. Wales was also part of this Great Britain since it had been absorbed by England by the 1536 Act of Union).
  • to dissolve both parliaments and replace them with a new Parliament of the Kingdom of Great Britain.

While there had been three earlier attempts to unite the two countries by Acts of Parliament, these were the first Acts which had the will of both political establishments behind them, albeit for rather different reasons. In the English case, the purpose was to establish the Royal succession along Protestant lines in the same manner as provided for by the English Act of Settlement rather than that of the Scottish Act of Security. In the Scottish case, the purpose was partly to recover from the financial problems caused by the failure of the Darien scheme and partly to remove English trade sanctions put in place to force the Scottish Parliament into compliance with the Act of Settlement.

The Acts of Union were not universally popular in Scotland, particularly amongst the general population. Many petitions were sent to the Scottish Parliament against union, and there were massive protests in Edinburgh the day it was signed. Many historians have since argued that the Scots Parliamentarians were co-erced into signing up for union by English bribery.

The Kingdom of Britain merged with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland on 1 January 1801. The United Kingdom shrank a little in 1922 when most of Ireland left to become the Irish Free State.