Helmut Friedrich Lachenmann (born 27 November 1935) is a German composer of contemporary classical music. His work has been associated with "instrumental musique concrète".

Lachenmann was born in Stuttgart and after the end of the Second World War (when he was 11) started singing in his local church choir. Showing an early aptitude for music, he was already composing in his teens. He studied piano with Jürgen Uhde and composition and theory with Johann Nepomuk David at the Musikhochschule Stuttgart from 1955 to 1958 and was the first private student of the Italian composer Luigi Nono in Venice from 1958 to 1960. He also worked briefly at the electronic music studio at the University of Ghent in 1965, composing his only published tape piece Szenario during that period, but thereafter focused almost exclusively on purely instrumental music. The brutality of his music led Francisco Estévez to compare his work to the paintings of Francis Bacon.