The Acts of Union were a pair of Parliamentary Acts passed in 1706 and 1707 by, respectively, the Parliament of England and the Parliament of Scotland, to put into effect the terms of the Treaty of Union which had been negotiated between the two countries. The Acts joined the Kingdom of England and the Kingdom of Scotland (previously separate states, with separate legislatures but with the same monarch) into a single Kingdom of Great Britain.

The two countries had shared a monarch for about 100 years (since the Union of the Crowns in 1603, when King James VI of Scotland inherited the English throne from his cousin, Queen Elizabeth I). Although described as a Union of Crowns, until 1707 there were in fact two separate Crowns resting on the same head. There had been three attempts in 1606, 1667, and 1689 to unite the two countries by Acts of Parliament, but it was not until the early 18th century that the idea had the will of both political establishments behind them, albeit for rather different reasons.

The Acts took effect on 1 May 1707. On this date, the Scots Parliament and the English Parliament merged to form the Parliament of Great Britain, based in the Palace of Westminster in London, the former home of the English Parliament (the parliaments of England and Scotland were dissolved ). Hence, the Acts are referred to as the Union of the Parliaments.

There was an attempt to rename Scotland and England as North and South Britain. This was generally short lived, particularly in "South Britain" - although the name "North Britain" lingered for a while in some institutions. This practice is now rarely, if ever seen.