The Celtic League is a group of people who all come from countries in Europe that have a special kind of culture and language called Celtic. They want these countries to work together and be treated fairly.
These countries are Ireland, Scotland, Wales, the Isle of Man, Cornwall, and Brittany. They all have a very old and interesting history that is very different from other countries in Europe.
The people in the Celtic League think that they should have more control over their own countries and not just be told what to do by bigger countries. They want to make sure their culture and languages are protected and not forgotten.
They also want to help each other out when there are problems, like if there is a big storm or if there is a disease that is hurting people.
So the Celtic League is like a big club that helps these countries work together and stand up for themselves.