The Copenhagen December Riot took place on 16 December 2006 in the Copenhagen area of Nørrebro. The spark of the riot was the longstanding conflict over the fate of the alternative left-wing social centre Ungdomshuset (The Youth House). The riot broke out when a Black Bloc demonstration in support of Ungdomshuset was blocked by the police. The riot was the worst of its kind in Copenhagen for at least 13 years and marked a low point in the negotiations between the authorities and the users of Ungdomshuset.
The riot is generally seen as the prelude to the much larger Copenhagen March Riot in 2007, which followed the eviction of Ungdomshuset on 1 March 2007.
In 1999, Ungdomshuset was put up for sale by the Copenhagen City Council. The house had originally been "given" to the city's community of squatters back in 1982 after the squatters had campaigned for an autonomous youth centre in Copenhagen. The agreement between the squatters and the city council was that the city authorities still officially owned the building but that the users of Ungdomshuset would be free to run the place as they saw fit, without interference from those authorities. Basic things such as paying rent still had to be meet by the users but otherwise the house would be completely autonomous and self-organized. The house soon became a gathering place for the city punk and alternative music scene and also became home to many political action groups as well as an underground performance scene.
Through the 1980s, conflict between the users and the city officials flared up. The users complained that about the city officials not keeping to their part of the agreement by demanding that the house live up to all kind of standards set by the city council. The city officials claimed that the users had no right to interfere with their work and said that Ungdomshuset had to live up to the standards set by the city council regarding public meeting places and daytime projects. The users replied by refusing to pay rent and retaliated by stating that Ungdomshuset was an autonomous social experiment and not a publicly run youth club or kindergarten. This made the city officials shut of the house supply of oil used for central heating. The users managed by installing wood fueled heating ovens in the major rooms of the house.
The tensions between the two sides increased through the 1980s and 1990s as the house developed into a centre for radical left-wing activities. The users of the house also became a thorn in the eye of the police as the users often were involved in clashes with these during demonstrations, evictions of squatted houses, etc. In 1987, the police mounted a raid on Ungdomshuset equipped with machine guns. The raid led to six arrests but since the police did not find anything illegal in the house they all were released without charges.