Line of Duty is a British police procedural television series created by Jed Mercurio and produced by World Productions. On 26 June 2012, BBC Two began to broadcast the first series; it was its best-performing drama series in ten years with a consolidated audience of 4.1 million viewers. Broadcast of the second series began on 12 February 2014; its widespread public and critical acclaim led to the BBC commissioning a further two series.^[1][2][3] The third series began on 24 March 2016 on BBC Two; the following three series were broadcast on BBC One.

In May 2017, the BBC commissioned a sixth series. Filming began in February 2020 but stopped the following month due to the COVID-19 pandemic; it resumed in September.^[4] Filming continued until November 2020.^[5] Broadcast of the sixth series began on BBC One on 21 March 2021.^[6]

Prior to switching channels from series four onwards, Line of Duty was the most popular drama series broadcast on BBC Two^[7] and is a winner of the Royal Television Society Award^[8] and Broadcasting Press Guild Award for Best Drama Series.^[9] The Telegraph included it in a list of the Top 50 BBC Two shows of all time^[10] and in a list of the 80 best BBC shows of all time.^[11] In 2016, the series ranked eighth in The Independent's list of the twenty greatest police shows of all time^[12] and third in a Radio Times 2018 poll of the best British crime dramas of all time.^[13] In 2021 Line of Duty won the National Television Award for Special Recognition.^[14]

Line of Duty follows DS Steve Arnott, an authorised firearms officer who is transferred to Anti-Corruption Unit 12 (AC-12) after refusing to agree to cover up an unlawful shooting by his own team. At AC-12 Arnott is partnered with DC Kate Fleming, a highly commended undercover officer with a keen investigative instinct. They work under the supervision of Superintendent Ted Hastings, uncovering corruption within the fictional Central Police. Throughout the series, AC-12 investigate seemingly disparate cases involving seemingly corrupt police officers such as DCI Tony Gates (series one), DI Lindsay Denton (series two), Sergeant Danny Waldron, DI Matthew Cottan, DCI Roseanne Huntley, undercover officer DS John Corbett and DCI Joanne Davidson.

AC-12 realises the pervasive nature of corruption and the police's deep-rooted links to an organised crime group. A long-running story arc revolves around discovering the identity of "H", a corrupt person or persons of senior rank within the police force who are instrumental in running organised crime.

Line of Duty was created and written by Jed Mercurio drawing inspiration from the Metropolitan Police anti-corruption unit A10, which was set up in 1971.^[15] The first two series were produced by World Productions, on behalf of BBC Two. David Caffrey and Douglas Mackinnon directed series one. Mackinnon directed the first three episodes of series two and Daniel Nettheim directed the remaining three episodes. Mercurio produced series one and acted as executive producer for series two, with Peter Norris taking over as producer for the second series.

Although the police refused to co-operate with the programme's producers, the production team was advised anonymously by serving officers and retired police officers, and made use of anonymous police blogs.^[16]

Following mixed reactions to the ending of the sixth series, there has been interest in seeing a further series produced.^[20] However as of 2024,^[update] production of a seventh series remains uncertain. Reports in late 2022 alleged that a three part mini-series had been proposed to air by Christmas 2023,^[21] however Mercurio has since stated he had "no news" regarding any development.^[22] Adrian Dunbar commented "There's a big appetite for more Line of Duty, it could be three or four episodes, I don't think there's going to be six for some reason. It might be two 90 minutes. We're all keeping our fingers crossed that we will hear something at some point. We all want to get back together, we'd love to go back to Belfast again."^[23][24] Martin Compston has since said that whilst the cast have confirmed their commitment to a potential seventh series, they remain focused on other projects.^[22] He also commented "Things are definitely things left open at the end of the series for it to continue…Because, look, people can have their opinions about the finale but this is the most successful drama in BBC history. So that could be a good place to end and walk away…All we've said is that we'd be up for doing [just] one more at some point but none of us have signed on".^[20]

Kew Media (previously known as Content Media) handled international distribution of the series^[25] until its collapse in 2020.^[26]

In Australia, as of 2021,^[update] the first five series are available across streaming services such as Britbox, Netflix, Acorn TV and Stan, but series six is exclusive to Britbox.^[41]

In the United States, the first series was released on Hulu in August 2012, as an exclusive series, until Acorn TV picked up the streaming rights for its platform in 2018, which included the existing series and exclusive access to series five and later additions.^[42][43] The first three series began airing on AMC on 4 April 2020.^[44][45] However, licence changes in 2021 led to BritBox also obtaining the rights to the series in the United States, along with exclusive rights to series six and any future series.^[46][47]