Liar is a British thriller television series created by Harry and Jack Williams, and co-produced by ITV and SundanceTV. The series stars Joanne Froggatt and Ioan Gruffudd as two people whose initial attraction leads to far-reaching consequences for them and their friends and families. The series premiered on ITV on 11 September 2017, with the first series concluding on 16 October 2017. Upon its debut, it received positive reviews, with many critics praising the performances of Froggatt and Gruffudd. The programme was renewed for a second and final series, which premiered on 2 March 2020, concluding on 6 April 2020.

Laura Nielson, a smart and capable teacher in the middle of a breakup, is set up on a date with widowed surgeon Andrew Earlham. However, the morning after, Laura realises she has been raped. When reporting the rape to the police proves fruitless, Laura investigates the incident herself.

Liar was announced on 15 April 2016 as the first full production from Two Brothers Pictures.^[3] On 30 September 2016, the miniseries was commissioned by American cable network SundanceTV and British commercial broadcaster ITV.^[4] Commercial broadcasters TF1^[5] and Seven have also ordered the series.^[6] Filming for the series began in London and Kent in November 2016.^[7] The marshes were filmed in Tollesbury, Essex. The seaside hometown for main character Laura was filmed at Deal, Kent and Kingsdown. Some inner town sequences in Brockley, Nunhead, Shortlands (Episode 3), South Ealing, and Edinburgh (Episode 4).^[8]

After the first series concluded on 16 October 2017, it was announced that the programme would be returning for a second series. The second series, which premiered on 2 March 2020,^[9] focuses on a whodunnit storyline involving the cliffhanger of the first series' finale. Froggatt and Gruffudd both returned.^[10][11][12]

The series premiered on ITV on 11 September 2017 at 9pm, in exactly the same slot that the Two Brothers Pictures series Rellik premiered on BBC One.^[14] It premiered on SundanceTV on 27 September 2017^[15] and is available for streaming on Sundance Now^[16] and YouTube.^[17] The series was acquired in Australia by the Seven Network and in New Zealand by TVNZ.^[18]

Up to nine remakes of Liar have been produced by networks in other countries, including India, Italy, Spain, Germany, France, Turkey, Greece, Slovakia and Malaysia. The Italian remake, Non mentire, premiered on Canale 5 on February 17, 2019.^[19] The Spanish remake, Mentiras, was first released on Atresplayer Premium on April 19, 2020, before eventually premiering on Antena 3 on January 12, 2022.^[20] The German remake, Du sollst nicht lügen, was first released on Joyn Plus+ on February 2, 2021, before debuting on pay television on Sat.1 Emotions on February 7 and premiering free-to-air on Sat.1 on February 9.^[21] The French remake, Mensonges, was first released on Salto on July 30, 2021, before premiering on TF1 on September 2, 2021.^[22] The Turkish remake, Yalanci, premiered on Show TV on September 17, 2021.^[23] The Greek remake, Psemata, premiered on Alpha TV on May 5, 2022.^[24] The Slovak remake, Klamstvo, premiered on Markíza on February 20, 2023.^[25] The Malaysian remake, "LIAR", was first released on Astro GO (on demand) on March 25, 2023, before premiering on Astro RIA on April 3, 2023.^[26] and Hindi as Marzi ^[27]