Etron Fou Leloublan, also known as EFL, were a French avant-garde rock band founded in 1973 by actor and saxophonist Chris Chanet. They recorded five studio albums between 1976 and 1985, and released a live album, En Public Aux Etats-Unis d'Amérique recorded during a tour of the United States in 1979. Etron Fou Leloublan were best known as one of the five original Rock in Opposition (RIO) bands that performed at the first RIO festival in London in March 1978.

Rock in Opposition or RIO was a movement representing a collective of progressive bands in the late 1970s united in their opposition to the music industry that refused to recognise their music. It was initiated by English avant-rock group Henry Cow in March 1978 when they invited four mainland European groups to come to London and perform in a festival called "Rock in Opposition".