Union Jack or Union Flag?

What do you call the UK’s national flag? Vexillologists know that either name is valid.

Download a comprehensive guide in Union Jack or Union Flag? An Official Flag Institute Guide.

Or for a short history please read on:

Union Jack or Union Flag? A Brief History

When first introduced in 1606, the ‘Union Jack’ was known simply as the ‘British flag’ or ‘flag of Britain’, and was ordered to be flown from the main masthead of all English and Scottish ships, warships and merchant ships.

The name ‘Union’ first appears in 1625, but what of the term ‘jack’?

Various theories exist, but the bulk of the evidence indicates use of the word in its diminutive sense. Before 1600, ‘jack’ was certainly used to describe a small flag flown from the mast mounted at the end of the bowsprit; by 1627, a small version of the Union flag – later described as the ‘Jack’, ‘Jack flag’ or ‘King’s Jack’ – seems to have flown commonly in this position; and by 1674, this flag was described formally as ‘His Majesty’s Jack’ and in common usage – officially acknowledged – as the Union Jack.


During the eighteenth century, the short mast on the bowsprit disappeared, to be replaced by staysails on the stays between bowsprit and foremast. The principal naval distinguishing flag had become the Ensign, so it grew customary to fly the Union Jack only in harbour – and from the ‘jackstaff’ (a specially rigged staff in the bows).

Note therefore that the ‘jack’ predated the ‘jackstaff’ by over 150 years, with the term ‘jack’ orginally denoting size rather than position.

It is sometimes claimed that the Union Flag should be described as the Union Jack only when flown in the bows of a warship, but this is a relatively recent idea. From its earliest days, the Admiralty often referred to the flag – however it was used – as the Union Jack. In 1902 an Admiralty Circular announced that either name could be used officially. And in 1908 the UK Parliament approved this verdict, stating that ‘the Union Jack should be regarded as the National flag’.

Cdr Bruce Nicolls OBE RN (Retd)