Ultras are a type of sports fans renowned for their fanatical support and elaborate displays. They are predominantly European followers of football teams. The behavioral tendency of ultras groups includes the use of flares (primarily in tifo choreography), vocal support in large groups and the displaying of banners at football stadiums, all of which are designed to create an atmosphere which encourages their own team and intimidates opposing players and supporters.

The actions of ultras groups can occasionally be overly extreme and are sometimes influenced by political ideologies or views on racism, in some instances to the point where the central ideology of the ultras phenomenon, passionate and loyal support of one's team, becomes a sideshow. In recent decades, the culture has become a focal point for the movement against the commercialization of sports and football in particular.

The origin of the ultras movement is disputed, with many supporters groups from various countries making claims solely on the basis of their dates of foundation. The level of dispute and confusion is aided by a contemporary tendency (mainly in Europe) to categorize all groups of overtly fanatical supporters as ultras. Supporters groups of a nature comparable to the ultras have been present in Brazil since 1939, when the first torcida organizada was formed. Inspired by the torcidas and the colorful scenes of the 1950 World Cup, supporters of Hajduk Split formed Torcida Split on 28 October 1950. The group is often cited as the oldest ultras/torcida style group in Europe.