National Action was a British right-wing extremist and neo-Nazi terrorist organisation based in Warrington. Founded in 2013, the group is secretive, and has rules to prevent members from talking about it openly. It has been a proscribed organisation in the United Kingdom under the Terrorism Act 2000 since 16 December 2016, the first far-right group to be proscribed since the Second World War. In March 2017, an undercover investigation by ITV found that its members were still meeting in secret. It is believed that after its proscription, National Action organised itself in a similar way to the also-banned Salafi jihadist Al-Muhajiroun network.

The Terrorism Act 2000 is the first of a number of general Terrorism Acts passed by the Parliament of the United Kingdom. It superseded and repealed the Prevention of Terrorism Act 1989 and the Northern Ireland Act 1996. It also replaced parts of the Criminal Justice Act 1998. The powers it provides the police have been controversial, leading to noted cases of alleged abuse, and to legal challenges in British and European courts. The stop-and-search powers under section 44 of the Act have been ruled illegal by the European Court of Human Rights.