Jón Sigurðsson, the 19th-century leader of Iceland's peaceful movement which ultimately brought independence from Denmark. This is the closest thing in the country to a carnival and is celebrated with parades, speeches, sport competitions, lots of outdoor entertainment and plenty of dancing.
The day tends to start off on a solemn and patriotic note, but by the afternoon the mood changes and the fun breaks out. Everyone takes the day off to be entertained by street performances, theatre, fire-eaters and to enjoy the real festival atmosphere.
Each town and village celebrates in their own way so it is advisable to check locally for details. This is such a popular date that it has been chosen for most major events of historical importance, the greatest being the establishment of the independent republic in 1944.
Have a look at this too, if you´d like to view some marvellous photos of today´s festivities: