Act of Union may be an act that refers to: In the United Kingdom:
- Laws in Wales Acts 1535–1542, passed by the Parliament of England, annexing Wales to the Kingdom of England are sometimes known as the "Acts of Union".
- Act of Union 1652, (more commonly know as the Tender of Union), annexation of Scotland by the Commonwealth of England
- Acts of Union 1707, passed by both the Parliament of England and the Parliament of Scotland to form the Kingdom of Great Britain.
- Act of Union 1800, passed by both the Parliament of Great Britain and the Parliament of Ireland to form the United Kingdom of Great Britain and Ireland.
- Act of Union 1840, passed by the Parliament of the United Kingdom, joining Upper Canada and Lower Canada (to form the Province of Canada).
- South Africa Act 1909, passed by the Parliament of the United Kingdom creating the Union of South Africa, is sometimes referred to as the Act of Union.
In Scandinavia:
- Act of Union 1814 forming a personal union between Sweden and Norway.
Other meanings
- An agreement between the Presbyterian and Congregationalist churches, within the United States.
- The term "act of union" is also used as a euphemism for sexual intercourse.
- The poem by Seamus Heaney, written in 1975.
