Kid A Mnesia is a reissue compiling the albums Kid A (2000) and Amnesiac (2001) by the English rock band Radiohead. It also includes a bonus disc, Kid Amnesiae, comprising previously unreleased material. It was released on 5 November 2021 on XL Recordings.

Kid A Mnesia was promoted with a campaign on the social network TikTok, followed by singles and music videos for the previously unreleased tracks "If You Say the Word" and "Follow Me Around". It was released to acclaim, though reaction to the bonus material was mixed. It entered the top 10 of several national album charts and topped the UK Independent Albums Chart and the US Billboard Top Alternative Albums and Top Rock Albums charts.

Kid A Mnesia Exhibition, an interactive experience with music and artwork from the albums, was released in the same month for PlayStation 5, macOS and Windows. A physical exhibition opened at the 2026 Coachella festival in California and is set to tour the US.

Radiohead recorded Kid A (2000) and Amnesiac (2001) simultaneously in 1999 and 2000. They originally considered releasing them as a double album, but felt the material was too dense. Kid A Mnesia compiles Kid A and Amnesiac, along with a third disc, Kid Amnesiae, comprising previously unreleased material from the Kid A and Amnesiac recording sessions. The albums are not remastered. The "deluxe" edition also contains an art book and Kid Amnesiette, a cassette edition with five B-sides.

"Like Spinning Plates ('Why Us?' Version)" is a piano arrangement of the electronic song "Like Spinning Plates". "If You Say the Word" features "delicate" fingerpicking, a "foreboding groove", "chiming" percussion and ondes Martenot. "Follow Me Around" is a solo acoustic guitar performance by Thom Yorke, with a "soaring" chorus and references to Margaret Thatcher. "Pulk/Pull (True Love Waits Version)" is a "harsh, industrial" version of another song, "True Love Waits", which Radiohead used to create the Amnesiac track "Pulk/Pull Revolving Doors". Kid Amnesiae also includes alternative versions of "Morning Bell" and the B-sides "Fog" and "Fast-Track", and isolated string tracks from "How to Disappear Completely" and "Pyramid Song".

On 1 April 2021, Radiohead joined the social media platform TikTok and began posting short videos featuring their character Chieftain Mews. Over the course of several months, they posted more than 30 videos. In early September, Radiohead posted a comedic video in which Yorke and Radiohead's cover artist, Stanley Donwood, discussed the channel's declining engagement.

Radiohead announced Kid A Mnesia on 7 September 2021, and released a digital single, the previously unreleased track "If You Say the Word". A music video for "If You Say the Word" was released on 23 September. Directed by Kasper Häggström, it follows two men who capture people in the forest and bring them to London to become office workers. "Follow Me Around" was released on 1 November, with a music video starring Guy Pearce as a man avoiding a drone following him in his home. Radiohead released Kid A Mnesia merchandise including a bone china tea set, and Yorke and Donwood produced two art books detailing the creative process of the albums. In October 2021, Donwood and Yorke curated an exhibition of Kid A artwork at Christie's headquarters in London.

Kid A Mnesia was released in vinyl, CD, cassette and digital versions. It reached number one on the UK Independent Albums Chart, number one the American Billboard Top Alternative Albums and Top Rock Albums charts, and the top ten of several other national charts.^{[citation needed]}