17 May celebrates the day in 1814 when Norway signed its constitution - the set of rules the country lives by. It says everyone is equal, everyone has rights, and the country belongs to all the people who live in it. Norway has had one of the world's oldest constitutions ever since.
Right from the start, the day was meant to be for the children. The first children's parade in the capital, Oslo, was organised in 1870 by a Norwegian writer who said that the future of the country belonged to its children. Today, every Norwegian town has its own children's parade. The biggest, in Oslo, has 80 schools marching past the royal palace.
Children wear their smartest clothes. Many wear a 'bunad' - a traditional Norwegian outfit, made of wool, embroidered with flowers, and different in every region of the country. The bunad worn by a child from the mountains looks different from the bunad worn by a child from the coast.
Throughout the day, families eat ice cream, hot dogs and waffles. Brass bands play. Norwegian flags are everywhere. The royal family stands on the balcony of the palace and waves at every single school as it passes. The whole country, big and small, is on the street.