Willem Andriessen (Haarlem, October 25, 1887 – Amsterdam, March 29, 1964) was a Dutch pianist and composer. His compositional output was small due to the demands of performance and teaching, but he was nonetheless awarded a number of compositional prizes in Belgium and the Netherlands.
He was an uncle of Louis Andriessen and Jurriaan Andriessen, who followed in his footsteps as composers.
Andriessen studied at the Amsterdam Conservatory, completing his studies in 1906, and was awarded the school's Outstanding Achievement Prize for piano. He appeared frequently in concert performances in the Netherlands, and was noted for his interpretations of J.S. Bach, Mozart, Beethoven and Robert Schumann, though he also played piano pieces from contemporaries such as Debussy, Ravel, Bartók and Pijper.
Andriessen taught at the Royal Conservatory in The Hague (1910–18) and following this at the Muziekschool in Rotterdam after 1924. He was appointed director of the Amsterdam Conservatory from 1937 to 1953. He also gave radio broadcasts of performances which included analyses of compositions. In 1942, following the Nazi occupation of the Netherlands, Andriessen and his brother Hendrik were imprisoned in Kamp Sint-Michielsgestel for a year, during which time Willem gave lecture-concerts for the prisoners.