Crass were an English art collective and punk rock band formed in 1977 who promoted anarchism as a political ideology, a way of life and a resistance movement. Crass popularised the anarcho-punk movement of the punk subculture, advocating direct action, animal rights, feminism, anti-fascism, and environmentalism. The band used and advocated a DIY ethic approach to its albums, sound collages, leaflets, and films.

Crass spray-painted stencilled graffiti messages in the London Underground system and on advertising billboards, coordinated squats and organised political action. The band expressed its ideals by dressing in black, military-surplus-style clothing and using a stage backdrop amalgamating icons of perceived authority such as the Christian cross, the swastika, the Union Jack and the ouroboros.

The band was critical of the punk subculture and youth culture in general. Nevertheless, the anarchist ideas that they promoted have maintained a presence in punk. Due to their free experimentation and use of tape collages, graphics, spoken word releases, poetry and improvisation, they have been associated with avant-punk and art punk.