It's a Sin is a British drama television miniseries written by Russell T Davies. Set in London between 1981 and 1991, it depicts the lives of a group of gay men and their friends during the HIV/AIDS crisis in the United Kingdom. It's a Sin features a main cast consisting of Olly Alexander, Omari Douglas, Callum Scott Howells, Lydia West, and Nathaniel Curtis. Other actors cast were David Carlyle, Keeley Hawes, Shaun Dooley, Tracy Ann Oberman, Neil Patrick Harris and Stephen Fry. The series was directed by Peter Hoar, produced by Red Production Company, and premiered in the United Kingdom on Channel 4 on 22 January 2021.

Its subject matter made the series a difficult sell to broadcasters. BBC One and ITV passed on the series, and Channel 4 took it on only after their commissioning editor of drama, Lee Mason, fought for it and the series was shortened from a planned eight episodes to five. Principal photography commenced on 7 October 2019. Despite its London setting, It's a Sin was filmed mainly in Manchester, with other locations used in Liverpool, Bolton, Eccles, Bangor, and Rhos-on-Sea. The series was executive produced by Davies, Hoar, and Nicola Shindler, with Phil Collinson serving as producer.

The show received critical acclaim for its emotional scenes, writing, performances and accurate depiction of HIV/AIDS. All episodes were released to Channel 4's online streaming service All 4 (now simply known as Channel 4), where it was viewed in its entirety more than 6.5 million times; making it the most binge-watched show to stream on the platform. The first episode also became Channel 4's biggest drama launch. The show was also credited for creating an upsurge in HIV testing in the weeks after its release. It was the most nominated show at the 2022 British Academy Television Awards, receiving eleven nominations, including Best Mini-Series.