Michael "Mike" "Monsieur Barso" Barson (born 21 April 1958) is a Scottish-born English musician and songwriter. He gained fame as the keyboardist for the ska/pop band Madness.
Born in Edinburgh, Barson grew up in North London with his two brothers Dan and Ben. He is often known by the nicknames "Monsieur Barso" or "Barzo".
Prior to forming Madness, Barson and fellow future Madness member Lee Thompson gained some notoriety as graffiti artists in the mid-1970s. After reading about the emerging New York graffiti scene, they spray-painted their nicknames ("Mr B" and "Kix") along with two friends' names "Cat" and "Columbo" around north London. They managed to spray their nicknames on George Melly's garage door, prompting Melly to write a newspaper article declaring: "If I ever catch that Mr B, Kix and Columbo, I’m going to kick their arses".
Barson co-founded a band called The Invaders in 1976. The band later changed their name to Madness after the song by Prince Buster.