The Acts of Union (Scottish Gaelic: Achd an Aonaidh) were two Acts of Parliament: the Union with Scotland Act 1706 passed by the Parliament of England, and the Union with England Act passed in 1707 by the Parliament of Scotland. They put into effect the terms of the Treaty of Union that had been agreed on 22 July 1706, following negotiation between commissioners representing the parliaments of the two countries. By the two Acts, the Kingdom of England and the Kingdom of Scotland—which at the time were separate states with separate legislatures, but with the same monarch—were, in the words of the Treaty, "United into One Kingdom by the Name of Great Britain".The two countries had shared a monarch since the Union of the Crowns in 1603, when King James VI of Scotland inherited the English throne from his double first cousin twice removed, Queen Elizabeth I. Although described as a Union of Crowns, and in spite of James's acknowledgement of his accession to a single Crown, England and Scotland were officially separate Kingdoms until 1707 (as opposed to the implied creation of a single unified Kingdom, exemplified by the later Kingdom of Great Britain). Prior to the Acts of Union there had been three previous 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 both political establishments came to support the idea, albeit for different reasons.

The Acts took effect on 1 May 1707. On this date, the Scottish Parliament and the English Parliament united to form the Parliament of Great Britain, based in the Palace of Westminster in London, the home of the English Parliament. Hence, the Acts are referred to as the Union of the Parliaments.