Pierre Mariétan (born 23 September 1935) is a Swiss composer.
Born in Monthey, Mariétan studied first at the Geneva Conservatory in 1955–60 with Marescotti and later with, amongst others, Pierre Boulez, Bernd Alois Zimmermann, Gottfried Michael Koenig, Henri Pousseur, and Karlheinz Stockhausen, and his earliest works are squarely in the serialist camp. During the 1960s he began creating outline sketches for improvisation, and beginning in the 1970s became increasingly interested in environmental sound and the problem of noise pollution.
In 1966 he was a founder of the Groupe d'Etude et Réalisation Musicales (GERM), and in 1979 founded the Laboratoire Acoustique et Musique Urbaine de l'Ecole d'Architecture de Paris La Villette, which he directed until 1990. Mariétan taught at the University of Paris (I et VIII) from 1969 to 1988 and at the Ecole d'Architecture de Paris la Villette in 1993. He was Director of the Conservatoire de Garges (Région parisienne) 1972–77, and has been a visiting lecturer at the Universities of Paris, Lille, Barcelona,Tokyo, Kyoto, Osaka, University of California San Diego, the Ecole Hautes Etudes Sociales Paris, Ecoles Nationales Supérieures des Beaux-Arts et d'Architecture of Paris, Besançon, and Marseilles, and the École Polytechnique de Lausanne.
While Mariétan's early work was primarily focussed on serialism, he turned in the 1960s to composing sketch-scores (some intended for amateurs and children) and guidelines for improvisation. Since the 1970s he has mainly focussed on combining composed music ("music of the interior"), with everyday environmental sounds ("music of the exterior"), which has led him to electronic and radiophonic composition. Paysmusique (1991), for example, combines 96 voices speaking in different Swiss dialects. He has also created sound installations and sound environments, sometimes collaborating with architects.