Crass was an English anarchist punk rock band, formed in 1977and based around Dial House, an open house community near Epping, Essex.

Whereas the Sex Pistols might have mentioned 'anarchy' for shock value (thereby furthering the common misconception that it is simply a synonym for chaos), Crass actually promoted genuine anarchism as a legitimate political ideology, way of living, and as a resistance movement, popularizing the seminal peace punk movement and touching on such overtly political issues as anti-consumerism, direct action, animal rights, feminism, anti-war, anti-corporatism, environmentalism, anti-globalization, anti-racism, squatting, and the separation of church and state.

Taking literally the punk manifesto of "Do It Yourself", Crass combined the use of sound collage, graphics, song, film, and subversion to launch a sustained and innovative critical broadside against all that they saw as a culture built on foundations of war, violence, sexism, prejudice, capitalism, religious hypocrisy and unthinking consumerism. They were also critical of what they perceived as the flaws of the punk movement itself, as well as wider youth culture in general. Crass were amongst the progenitors of the anarcho-pacifism that became common in the punk music scene.

From their earliest days of spraying stencilled anti-war, anarchist, feminist and anti-consumerist graffiti messages around the London Underground system and on advertising billboards. the band had always been involved in political as well as musical activities. On December 18th, 1982, Crass co-ordinated a 24 hour squat of the Zig Zag club in West London primarily for an all day event attended by approximately 500 people to prove "that the underground punk scene could handle itself responsibly when it had to and that music really could be enjoyed free of the restraints imposed upon it by corporate industry".

In 1983 and 1984 they were part of the Stop the City actions instigated by London Greenpeace that were arguably fore-runners of the anti-globalisation actions of the early 21st century.

Explicit support for such activities was given in the lyrics of the band's final single release "You're Already Dead", which also saw Crass abandoning their long time commitment to pacifism. This led to further introspection within the band, with some members feeling that they were beginning to become embittered as well as losing sight of their essentially positive stance.