"Karma Police" was released as the second single from OK Computer on 25 August 1997. The single was released in two versions. The single peaked at number eight on the UK Singles Chart and at number fourteen on the US Hot Modern Rock Tracks. In late March 2010, almost thirteen years after its initial single release, the song went to number fifteen on the Danish Singles Chart. In a song review, Allmusic referred to Karma Police as "haunting, mystifying, and exquisite" labelling it "one of the cornerstones of one of the greatest albums of the '90s."
The song's title and lyrics derive from an in-joke among the band, referring to the Hindu theory of retributive enforcement, karma.
Radiohead members used to tell one another that they would call "the karma police" on them if they did something wrong. The joke was incorporated as into the lyrics and title of the song. Yorke explained that the song was about stress and "having people looking at you in that certain [malicious] way, I can't handle it anymore". Thom Yorke explained the idea of the lyrics to The Independent in 2006, saying, "It's for someone who has to work for a large company. This is a song against bosses. Fuck the middle management!" Yorke and Jonny Greenwood emphasised in interviews that the song had a humorous bent; Yorke said, "[It's] not entirely serious, I hope people will realize that." The song includes the line "He buzzes like a fridge/He's like a detuned radio", a reference to the distracting, metaphorical background noise Yorke calls "fridge buzz". Yorke has said that the idea of fridge buzz is one of the primary themes of OK Computer; "Karma Police" also shares themes of insanity and dissatisfaction with capitalism.
The music video for the song was directed by Jonathan Glazer, previously responsible for Radiohead's "Street Spirit (Fade Out)" clip. The video premiered in August 1997 and featured Radiohead frontman Thom Yorke as well as Hungarian actor Lajos Kovács. Glazer won MTV's Director of the Year award in 1997 for his work on this. Glazer however revealed in an interview that he considers this video to be a failed attempt. According to MTV.com, Glazer had pitched the concept of the "Karma Police" video months earlier to Marilyn Manson, who disliked it.