Why does the flag have 12 stars? Some people think that each star represents a country. But that is not true.
Last year there were 15 countries in the EU. Then 10 more countries joined this year. Even more countries will be joining in the years ahead.
So the number of stars on the flag has nothing to do with the number of countries in the EU.
The flag has 12 stars because the number twelve is the symbol of completeness and unity.
In various traditions, twelve is a symbolic number representing perfection. It is also the number of months in a year and the number of hours shown on a clock face. The circle is a symbol of unity.
So it was decided to put 12 stars in a circle on the European flag, representing unity among the peoples of Europe.
The history of the flag goes back to 1955 when there were just six countries in the organisation that would eventually become the European Union.
Another organisation called the Council of Europe suggested using a flag with a circle of twelve gold stars on a blue background.
Eventually everyone agreed, and now everyone in the EU uses this flag.
If you live near a new motorway in Ireland, you may see the flag on a big sign beside the road. This means that the European Union gave some money to Ireland to help build the motorway.