By Luke Dalton. Updated 10 July 2026.

In 30 seconds: both names are correct. The Flag Institute, the UK's recognised authority on flags, states that the national flag of the United Kingdom is the Union Flag, which may also be called the Union Jack. An Admiralty Circular ruled in 1902 that either name could be used officially, and in 1908 a government minister told Parliament that the Union Jack should be regarded as the national flag. The names have been officially interchangeable for more than 120 years. Everything below is the history, the evidence, and the answer to every version of this argument we have seen in our comments.

Why This Argument Never Dies

We launched a national Union Jack billboard campaign this month, and within hours the comment sections filled with the same argument Britain has been having for a century: it is the Union Flag, not the Union Jack, and anyone who says otherwise, including apparently a company founded by Royal Marines, has embarrassed themselves. One commenter told us that a Royal Marine veteran letting his team say Union Jack was a quality control failure.

It is a great British argument because it feels like insider knowledge. The "it is only a Jack at sea" rule gets passed around as the mark of someone who really knows their flags. There is just one problem with it: the actual authorities on British flags say it is wrong, and they have said so for a very long time.

The Official Answer

The Flag Institute is the UK's vexillological charity and the recognised body on British flags, and its guidance could not be plainer: the national flag of the United Kingdom is the Union Flag, which may also be called the Union Jack. Not "which is incorrectly called". May also be called.

The paper trail goes back well over a century. In 1902, an Admiralty Circular announced that either name could be used officially. In 1908, a government minister told Parliament that the Union Jack should be regarded as the national flag. So the highest naval authority in the land and Parliament itself both signed off on the name more than 120 years ago. If you are correcting people in comment sections, you are not defending a rule. You are defending a rule that was overruled in 1902.

Where "Jack" Comes From

The honest answer is that nobody is completely certain, which is part of why the argument survives. The most common explanation ties the word to the sea: a jack is a small flag flown from the jack staff at the bow of a warship, and the Union Flag flown there became the Union Jack. From that comes the purist position that the name only applies afloat. It is a tidy theory, and the usage historians point out that "Union Jack" has been used freely on land as well as at sea for centuries. The name stuck because the country liked it, and in 1902 officialdom stopped fighting it.

A Two Minute History of the Flag

The flag exists because one king inherited multiple crowns. In 1603, James VI of Scotland became James I of England, and in 1606 a royal proclamation created the first Union Flag, combining England's red cross of St George with Scotland's white saltire of St Andrew. That flag flew for nearly two centuries.

The flag you know today dates from 1801, when the red saltire of St Patrick was added to represent Ireland after the Acts of Union. Three crosses, three patron saints, one flag. It also, as the Flag Institute drily notes, made it possible for the first time to fly the flag upside down, which is a story we cover properly in our guide to flying the Union Jack the right way up.

Why Is Wales Not on the Union Jack?

The most asked follow-up question, and a fair one. Wales is not separately represented because Wales had already been annexed into the Kingdom of England under the Laws in Wales Acts of 1535 and 1542, decades before the first Union Flag was created in 1606. As far as the flag makers of 1606 were concerned, the cross of St George already covered Wales. Whether that still feels right in 2026 is a live debate, and proposals to add the Welsh dragon surface every few years. For now, the flag remains the three crosses of 1801.

What the Crosses Mean

Three crosses overlaid: the red cross of St George edged in white for England, the white diagonal saltire of St Andrew on blue for Scotland, and the red diagonal saltire of St Patrick for Ireland, now representing Northern Ireland. The design is deliberately asymmetric where the two saltires meet, which is why the flag has a correct way up. One more thing worth knowing: there is no Flag Act in UK law. The Union Flag is the national flag by long established custom and practice, not by statute, which is very British when you think about it.

The Comment Section Rulebook

So here is the rulebook for the next time this kicks off under one of our posts. Calling it the Union Jack: correct. Calling it the Union Flag: correct. Telling a veteran owned coffee company that it named its own national flag wrong: incorrect since 1902. We answered every one of those comments the same way, and it is the same answer that sits under our whole campaign: we are proud to be British, proud to have served, and proud to fly the flag. Whichever name you use for it.

Frequently Asked Questions

Is it the Union Jack or the Union Flag?

Both are correct. The Flag Institute states that the national flag of the United Kingdom is the Union Flag, which may also be called the Union Jack. The names have been officially interchangeable since an Admiralty Circular of 1902, and in 1908 Parliament was told the Union Jack should be regarded as the national flag.

Is it wrong to say Union Jack on land?

No. The idea that the flag is only a Jack when flown at sea is a popular belief, but the Flag Institute confirms both names are acceptable in all contexts, and the name Union Jack has been used on land for centuries.

Why is it called a Jack at all?

The most common explanation is naval: a jack is a small flag flown from the jack staff at the bow of a warship, and the Union Flag flown there became known as the Union Jack. The true origin is not certain, but the name has been in general use at sea and on land for centuries.

When was the Union Jack created?

The first Union Flag was created by royal proclamation in 1606, after James VI of Scotland became James I of England, combining the crosses of St George and St Andrew. The present design dates from 1801, when the red saltire of St Patrick was added to represent Ireland.

Why is Wales not on the Union Jack?

Wales had already been annexed into the Kingdom of England under the Laws in Wales Acts of 1535 and 1542, before the first Union Flag was created in 1606, so it was considered covered by the cross of St George. Proposals to add Welsh representation surface regularly, but the design remains the three crosses of 1801.

What do the three crosses on the flag represent?

The red cross of St George represents England, the white diagonal saltire of St Andrew on blue represents Scotland, and the red diagonal saltire of St Patrick represents Ireland, now Northern Ireland.

Is the Union Jack the official national flag by law?

There is no Flag Act in UK law. The Union Flag is the national flag of the United Kingdom through long established custom and practice, reinforced by the 1908 statement in Parliament that it should be regarded as the national flag.

Does the Union Jack have a right way up?

Yes. The design is asymmetric, and in the half of the flag nearest the flagpole the wider white diagonal stripe must sit above the red diagonal. Our guide to flying the Union Jack covers the rule, the upside down myth and the actual regulations in full.

Related Guides

• The Union Jack Billboard Campaign: They took the flags down, so we put ours on more than 40 digital screens across Britain. The full story.
• How to Fly the Union Jack: The Right Way Up: The correct orientation, the upside down myth, and the rules that actually exist.
• Best Military Coffee UK: The veteran and forces coffee brands actually worth buying.
• The Red On Range: Our strongest line in every format: coffee, brew bags, cans and caffeine pouches.

References and Further Reading

• The Flag Institute: Union Jack or Union Flag? Authoritative advice
• The Flag Institute: British flag protocol (Flying Flags in the United Kingdom)
• Wikipedia: Union Jack (history, design and the position of Wales)