Ultras are a type of association football fans who are renowned for their fanatical support. The term originated in Italy, but is used worldwide to describe predominantly organised fans of association football teams. The behavioural tendency of ultras groups includes their 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 the opposing players and their supporters. The frequent use of elaborate displays in stadiums is also common.

Ultras groups and their actions are extreme and they are influenced and directly linked to nationalism and patriotic behaviors. In some instances, this goes to the point where the passionate and loyal support of one's team becomes secondary to the theoretical ideology of the ultras phenomenon. In recent decades, the culture has become a focal point for the movement against the commercialisation of sports and football in particular. Ultras also have regional variants and analogues, such as the barra bravas in Hispanic America and Torcidas Organizadas in Brazil.