Carl Smyth, also known as Chas Smash (born Cathal Joseph Patrick Smyth, January 14, 1959, in Middlesex Hospital, London, England), is an English born musician of Irish immigrant parents, best known as a backing singer and dancer in the 2 Tone ska/pop band Madness. He also plays trumpet, acoustic guitar and various percussion instruments. He also occasionally performs lead vocals. He was an occasional songwriter, becoming a more regular contributor over the course of Madness' career, and was credited as co-writer on the group's major international hit, Our House.

In 1976, The North London Invaders recruited Smyth to play bass until he was replaced in 1977 by Gavin Rogers. In late 1979, Smyth became the last of the seven original Madness members to join the band. Prior to that he was a friend of the band members and danced onstage at concerts. After Madness broke up in 1986, he formed a new shortlived band, The Madness, with Graham McPherson (Suggs), Lee Jay Thompson and Chris Foreman. In the early 1990s, Smyth became an executive for Go Discs and was responsible for reforming the original Madness in 1992 for Madstock!. During the late 1980s, he became good friends with former Smiths' vocalist Morrissey, who once asked him to be his manager. Smyth declined, claiming "I didn't fancy having to iron his socks". He provided backing vocals on Morrissey's version of The Jam's "That's Entertainment". Smyth had a small part in Suggs' solo career, co-writing the song Green Eyes and appearing in the video for I'm Only Sleeping. Smyth led the folk-influenced band Velvet Ghost, which was most active in the early 2000.

In 2002, Smyth started up his own record label, RGR Music, at an office in Camden Town. He released a debut single, We're Coming Over, with The England Supporters Band (billed as Mr. Smash & Friends), and it reached # 60 in the UK Singles Charts. RGR released an album and three singles by London rapper, Just Jack. The label also released material by dance and rap artists Autamata and Border Crossing, but none of the releases charted. In 2004, after briefly moving his office to Islington, Smyth closed RGR and started to concentrate more on his Madness projects. In summer 2006, Madness toured Europe and Japan in support of The Dangermen Sessions Vol. 1. Following those tours, Madness began recording their first original album since 1999's Wonderful. Smyth currently lives in North London with his children