Marguerite Long (13 November 1874 – 13 February 1966) was a French pianist and teacher.
Marguerite Marie-Charlotte Long was born in Nîmes. She studied with Henri Fissot at the Paris Conservatoire, taking a premier prix in 1891, and privately with Antoine François Marmontel. From 1906 to 1940 she taught at the Paris Conservatoire, and in 1920 she succeeded Louis Diémer as professor of piano. She also taught privately. Her students included Cemal Reşit Rey, Jacques Février, Samson François, Georges Savaria, Gabriel Tacchino, Zvart Sarkissian, Jean Doyen, Monique Duphil, Marie-Thérèse Fourneau, Waleed Hourani, Willem Ibes, and Micheline Laudun Denis.
Long's husband, Joseph de Marliave (1873–1914), was killed in August 1914 in action during World War I. Maurice Ravel dedicated the last section, the Toccata, of Le Tombeau de Couperin to him. Marguerite Long gave the first performances of this work in 1919, and in January 1932 the premiere of Ravel's Piano Concerto in G major, which was dedicated to her.
In 1943 she and violinist Jacques Thibaud established the Marguerite Long-Jacques Thibaud International Competition for violinists and pianists, which takes place each year in Paris. Since 2011, the competition has included singers and it is now known as the Long-Thibaud-Crespin Competition, in honour of the soprano Régine Crespin.
Marguerite Long died in Paris in 1966, aged 91.
- Dunoyer, Cecilia, Marguerite Long: a Life in French Music, 1874–1966, 1993) (with discography)
- Long, Marguerite, Au piano avec Claude Debussy, 1960 (Eng. 1972)
- —, Le Piano, 1959
- —, La Petite Méthode de piano, 1963
- —, Au piano avec Gabriel Fauré, 1963 (Eng. 1980)
- Long, Marguerite and with Pierre Laumonier, Au piano avec Ravel, 1971 (Eng. 1973)
- Weill, Janine, Marguerite Long: une vie fascinante, 1969