The Animal Liberation Front (ALF) is a name used internationally by animal liberation activists who engage in direct action on behalf of animals. This includes removing animals from laboratories and fur farms, and sabotaging facilities involved in animal testing and other animal-based industries. According to ALF statements, any act that furthers the cause of animal liberation, where all reasonable precautions are taken not to endanger life, may be claimed as an ALF action. Best, Steven & Nocella, Anthony J. (eds), Terrorists or Freedom Fighters?, Lantern Books, 2004, p. 8.

The ALF is not a group with a membership, but an example of a leaderless resistance, a banner for activists to use. ALF volunteers see themselves as the modern equivalent of the Underground Railroad, the 19th-century anti-slavery network, with activists removing animals from laboratories and farms, arranging safe houses and veterinary care, and operating sanctuaries where the animals live out the rest of their lives. Covert cells, active in 37 countries, operate clandestinely and independently of one another, with activists working on a need-to-know basis. ALF cells are known to be active in Argentina, Australia, Austria, Belgium, Belarus, Brazil, Canada, Canary Islands, Chile, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Holland, Iceland, Ireland, Israel, Italy, Malaysia, Mexico, New Zealand, Norway, Poland, Portugal, Romania, Russia, Slovakia, Spain, Sweden, Switzerland, Turkey, United Kingdom, United States. See blank">"Diary of Actions", Bite Back, March 10, 2008. A cell might consist of just one person. _Robin Webb, who runs the Animal Liberation Press Office in the UK, has said: "That is why the ALF cannot be smashed, it cannot be effectively infiltrated, it cannot be stopped. You, each and every one of you: you are the ALF." blank">"Staying on Target and Going the Distance: An Interview with U.K. A.L.F. Press Officer Robin Webb", No Compromise, Issue 22, undated

Activists who speak on behalf of the ALF say the movement is non-violent. In _Behind the Mask, a 2006 documentary, American activist Rod Coronado said: "One thing that I know that separates us from the people we are constantly accused of being — that is, terrorists, violent criminals — is the fact that we have harmed no one." Behind the Mask: The Story Of The People Who Risk Everything To Save Animals, a film by Shannon Keith, 2006. There has nevertheless been widespread criticism that ALF spokespersons and activists have either failed to condemn acts of violence or have themselves engaged in it. The Southern Poverty Law Center (SPLC), which monitors U.S. domestic extremism, has noted the involvement of ALF activists in the Stop Huntingdon Animal Cruelty campaign, which SPLC identifies as using "frankly terroristic tactics similar to those of anti-abortion extremists," blank">"From Push to Shove", _Southern Poverty Law Center Intelligence Report, Fall 2002. and in January 2005, the ALF was described as a domestic terrorist threat by the United States Department of Homeland Security.