Marcelle Mercenier (1920 – 13 March 1996) was a Belgian pianist and teacher. Mercenier was known as an influential pedagogue in Brussels, then in Liège. She was a fervent advocate of contemporary music, but also performed Chopin under the baton of Charles Munch and Poulenc with the composer (Friche 1996). She was a member of the group "Séminaire des Arts" created in August 1944 in Brussels. In the concert series of this group, on 28 February 1947 she premiered, together with the flautist Herlin Van Boterdael, the Sonatina for flute and piano by Pierre Boulez, a work that had been composed a year earlier for Jean-Pierre Rampal, but had not been performed by him (Gärtner 2002, 54). The Sonatine was the second work in which Boulez used serial technique, after the Notations for piano of 1945 (Hopkins and Griffiths 2011). She also gave the first Belgian performance of the final version of Boulez's Third Piano Sonata and premiered works by Karlheinz Stockhausen, Henri Pousseur, and Philippe Boesmans.