Louis Andriessen (Dutch pronunciation: [luˈi ˈɑndrisə(n)]; born 6 June 1939) is a Dutch composer and pianist based in Amsterdam. He is a lecturer at the Royal Conservatory of The Hague. He was recipient of the Gaudeamus International Composers Award in 1959.
Andriessen was born in Utrecht into a musical family, the son of the composer Hendrik Andriessen (1892–1981), brother of composers Jurriaan Andriessen (1925–1996) and Caecilia Andriessen (born 1931), and nephew of Willem Andriessen (1887–1964).
Andriessen originally studied with his father and Kees van Baaren at the Royal Conservatory of The Hague, before embarking upon two years of study with Italian composer Luciano Berio in Milan and Berlin. He later joined the faculty of the Royal Conservatory. See: List of music students by teacher: A to B#Louis Andriessen.
In 1969 Andriessen co-founded STEIM in Amsterdam. He also helped found the instrumental groups Orkest de Volharding and Hoketus, both of which performed compositions of the same names. He later became closely involved in the ongoing Schonberg and Asko ensembles and inspired the formation of the British ensemble Icebreaker.