So, a long, long time ago in France, there was a king named Louis XIV. He was very powerful and had a lot of control over the people in his country.
Now, King Louis XIV was a Catholic and he wanted everyone to be Catholic too. But, there were some people in France who were not Catholic - they were Protestants.
King Louis XIV did not like the Protestants and wanted them to become Catholic. So, he created something called the Edict of Fontainebleau.
This edict was a very important law that said that all the Protestants in France could not practice their religion anymore. They could not have their own churches, they could not read the Bible in public or even in private, and they could not teach their children about their religion.
This was a really big deal because it took away people's right to practice their own beliefs and religion. It was like taking away a toy from a child - they were upset and angry.
Many Protestants had to leave France to go to other countries where they could practice their religion freely. It was really sad for them and their families.
So, the Edict of Fontainebleau was a law made by King Louis XIV that said Protestants could no longer practice their religion in France. It was not a very nice thing to do and it caused a lot of pain and suffering for many people.