The Union Jack or Union Flag is the de facto national flag of the United Kingdom. The Union Flag was also used as the official flag of several British colonies and dominions before they adopted their own national flags. The flag continues to have official status in Canada, by parliamentary resolution, where it is known as the Royal Union Flag.
A portrait of a ship, with the Union Jack placed on a jackstaff at the ship's bow, 1637
A portrait of King George III in 1800. A proclamation by George III in 1801 refers to the design as the Union Flag.
The Linlithgow Palace carving with a proposed flag of the new Union of the Crowns, c. 1617
Slezer's Edinburgh Castle c. 1693 depicting the Scottish Union flag
Flag of the United Kingdom
The national flag of the United Kingdom is the Union Jack, also known as the Union Flag.
Mural in Belfast explaining the origin of the Union Flag.