The third series of the British police procedural television programme Line of Duty, was broadcast on BBC Two between 24 March and 28 April 2016.

AC-12 is led by Superintendent Ted Hastings (Adrian Dunbar), who is assisted by his team, DS Steve Arnott (Martin Compston), DC Kate Flemming (Vicky McClure), and DI Matthew "Dot" Cottan (Craig Parkinson).

Supporting characters include Gill Biggeloe (Polly Walker), Chief Superintendent Terry Reynolds (Shaun Parkes), DS Sam Railston (Aiysha Hart), Joe Nash (Jonas Armstrong), Maneet Bindra (Maya Sondhi), Chief Superintendent Patrick Fairbank (George Costigan), and DC Nigel Morton (Neil Morrissey).

[10] Keeley Hawes, who starred in series two as DI Lindsay Denton, initially stated that she would not return to Line of Duty due to her conflicting filming on the Fungus the Bogeyman television adaptation.

[13] Mercurio later decided to bring Hawes back to the series as a result of Denton's positive reception and made changes to a script to allow for Waldron's death.

[14] Other supporting cast members include the returning Neil Morrisey[16] and newcomers Polly Walker, Shaun Parkes, Aiysha Hart, Jonas Armstrong, Maya Sondhi, and George Costigan.

[22] Filming locations included BT Riverside Tower, McHugh's Bar, Belfast City Hall, and Invest Northern Ireland.

[47] Reviewing the series premiere for Den of Geek, Louisa Mellor wrote about how Waldron's character developed from being just dirty cop to a victim as well, and how this deceit was a result of Mercurio's depth of writing Mays' acting.

[49] Hawes's return as Denton was praised by many critics who noted the passion and complexity behind the performance as well as her unexpected death.

[58] A former Metropolitan Police homicide detective criticised the accuracy of the series, stating that it "suggests a culture where fatal shootings are not thoroughly investigated and where dangerous officers can be re-issued with firearms.