Cardiacs are an English rock band formed in Kingston upon Thames by Tim Smith (guitar and lead vocals) and his brother Jim (bass, backing vocals) in 1977 under the name Cardiac Arrest. One of Britain's leading cult rock bands, Cardiacs' sound folded in genres including art rock, progressive rock, art punk, post-punk, jazz, psychedelia and heavy metal (as well as elements of circus, baroque pop, medieval music, nursery rhymes and sea shanties), all of which was topped by Smith's anarchic vocals and hard-to-decipher lyrics. The band's theatrical performance style often incorporated off-putting costumes and make-up, complete with on-stage confrontations. Their sound and image made them unpopular with the press, but they amassed a devoted following.

Tim Smith was the primary songwriter, noted for his complex and innovative compositional style. He and his brother were the only constant members in the band's regularly changing lineup. The band created their own indie label, the Alphabet Business Concern, in 1984 and found mainstream exposure with the single "Is This the Life" from their debut album A Little Man and a House and the Whole World Window (1988). Their second album, On Land and in the Sea (1989), was followed by Heaven Born and Ever Bright (1992), which displayed a harder edged, metal-leaning sound retained in the subsequent albums Sing to God (1996) and Guns (1999). The final Cardiacs album, LSD, was left unfinished after Tim Smith was hospitalised with dystonia resulting from a cardiac arrest and stroke in 2008, which caused the band to go on hiatus until the release of the album in 2025.

Smith's illness brought increased and belated critical recognition to Cardiacs, with several music outlets calling Sing to God a masterpiece. His death in 2020 saw a raft of tributes on social media. Many rock groups including Blur were influenced by Cardiacs' eclectic music, which appeared on streaming services in 2021. Billed as Cardiacs Family & Friends, or sometimes just Cardiacs, Cardiacs members "past, present, and future" performed the music of Tim Smith at several sold-out gigs in 2024. After the release of LSD, Cardiacs announced three live dates in support of the album for March 2026.

Cardiacs originated in Kingston upon Thames, Surrey, in the late 1970s. Frontman Tim Smith began his musical career in 1975 after forming a nameless band at school in which he played guitar. Smith played his first gig at Surbiton Assembly Rooms aged 16 alongside Adrian Borland of the Outsiders and drummer Bruce Bisland as Gazunder. The Cardiacs biography describes their two gigs in 1976 as sounding "a bit like the rocky instrumental bits" on David Bowie's The Man Who Sold the World (1970). The band that would become Cardiacs was formed in late 1977 by Smith and his brother Jim on bass guitar and backing vocals, alongside Michael Pugh on lead vocals and Peter Tagg on drums. The project was initially called the Filth, but soon changed their name to Cardiac Arrest, possibly by their second gig in 1978 according to Tagg. According to the official history, Tim Smith formed the band merely to punish his brother "for all the unkind things he would do to him as an infant", as Jim allegedly couldn't play an instrument.

Cardiac Arrest produced a demo in 1977, and released their debut single "A Bus for a Bus on the Bus" in 1979 under Tortch Records. Peter Tagg and Ralph Cade decamped from Cardiacs and formed the Trudy. Smith, the primary lyricist, initially took on guitar and backing vocal duties before Pugh's departure saw him promoted to frontman. Cardiac Arrest followed the single with a full-length cassette release titled The Obvious Identity in 1980, which was released at around 1000 copies exclusively sold at concerts. Shortly after, the group went through a number of name changes, settling on simply Cardiacs in 1981. They held their first concert under the new name in April.

In 1981, Cardiacs self-released the cassette album, Toy World, featuring both new material and recordings dating back to the Cardiac Arrest period. (Consequently, some tracks featured Michael Pugh as lead singer rather than Tim Smith). During 1981, Colvin Mayers left the band to join the Sound, a group led by Borland. Sarah Cutts briefly covered live keyboards as well as saxophone, before Mark Cawthra swapped drums for keyboards and Dominic Luckman was recruited from the road crew as the new drummer. At around the same time percussionist Tim Quy became a full-time member (also doubling on bass synthesizer). In July 1983, Tim Smith married Sarah Cutts – taking his surname, she was henceforward known as Sarah Smith.

In mid-1983 Mark Cawthra left the band, to be replaced on keyboards by William D. Drake. Tim Smith had previously met Drake in 1982 at the debut performance of Drake's band Honour Our Trumpet (who promptly invited him to join as bass guitarist.) Following Cawthra's departure, Smith returned Drake's favour by inviting him to join Cardiacs. Drake played his first concert with the band on 31 August 1983. Later in the year, Cardiacs added Marguerite Johnston (alto saxophone) and Graham Simmonds (guitar), and for about a year the band worked as an octet. Both Johnston and Simmonds left during the following summer (in July and August respectively), although Simmonds stayed on as Cardiacs' sound engineer. At some point in 1983, Tim Smith produced two issues of a comic alternatively called "Peter and His Dog" and "Peter and His Dog Spot".

By autumn 1984, the band lineup had settled as the sextet generally referred to as "the classic lineup" – Tim Smith (lead vocals and guitar), Jim Smith (bass and vocals), William D. Drake (keyboards and vocals), Sarah Smith (saxophones and vocals), Tim Quy (percussion and keyboards) and Dominic Luckman (drums). The first Cardiacs release featuring the "classic" lineup was their third album, The Seaside (although Cawthra featured throughout on drums, keyboards and voice; and Simmonds and Johnston also appeared on several tracks). The album was released on Cardiacs own record label, Alphabet (which later became Alphabet Business Concern). The bizarre and sinister "Alphabet Business Concern" mythology now began to become a significant part of Cardiacs' artistic presentation, and the band members would promote and add to it at every opportunity. The band evolved an elaborate and theatrical stage show, involving off-putting "bandsmen's uniforms, makeup, Sarah's music stand, (and) Tim's mile-wide grin".