Charles Louis Eugène Koechlin (French pronunciation: ​[ʃaʁl lwi øʒɛn keˈklɛ̃]; 27 November 1867 – 31 December 1950) was a French composer, teacher and writer on music. He was a political radical all his life and a passionate enthusiast for such diverse things as medieval music, The Jungle Book of Rudyard Kipling, Johann Sebastian Bach, film stars (especially Lilian Harvey and Ginger Rogers), traveling, stereoscopic photography and socialism. He once said: "The artist needs an ivory tower, not as an escape from the world, but as a place where he can view the world and be himself. This tower is for the artist like a lighthouse shining out across the world."
Koechlin was born in Paris, and was the youngest child of a large family. His mother's family came from Alsace and he identified with that region; his maternal grandfather had been the noted philanthropist and textile manufacturer Jean Dollfus, and Koechlin inherited his strongly developed social conscience. His father died when he was 14. Though he was early interested in music his family wanted him to become an engineer. He entered the École Polytechnique in 1887 but the following year was diagnosed with tuberculosis and had to spend six months recuperating in Algeria. He had to repeat his first year at the École and graduated with only mediocre grades. After a struggle with his family and private lessons with Charles Lefebvre he entered the Paris Conservatoire in 1890 studying first with Antoine Taudou for harmony. In 1892 he started studying with Massenet for composition, André Gedalge for fugue and counterpoint, and Louis Bourgault-Ducoudray for musical history. His fellow-pupils included George Enescu, Ernest Le Grand, Reynaldo Hahn, Max d'Ollone, Henri Rabaud and Florent Schmitt. From 1896 he was a pupil of Gabriel Fauré, where his fellow-pupils now included Ravel and Jean Roger-Ducasse. Fauré had a major influence on Koechlin; in fact Koechlin wrote the first Fauré biography (1927), a work which is still of value. In 1898 a grateful Koechlin orchestrated the popular suite from Fauré's Pelléas et Melisande music and in 1900 assisted Fauré in the production of the huge open-air drama Promethée.

After his graduation Koechlin became a freelance composer and teacher. He married Suzanne Pierrard in 1903, but after 1921 regularly corresponded with his former student, composer Catherine Murphy Urner in California. In 1909 he began regular work as a critic for the Chronique des Arts and in 1910 was one of the founders, with Ravel, of the Société musicale indépendante, with whose activities he was intensely associated. From its inception in the early 1930s to his death he was a passionate supporter of the International Society for Contemporary Music, eventually becoming President of its French section. From 1937 he was elected President of the Fédération Musicale Populaire. At first comfortably off, he divided his time between Paris and country homes in Villers-sur-Mer and the Côte d'Azur, but after the onset of World War I his circumstances were progressively reduced, he was forced to sell one of his houses and, from 1915, took work lecturing and teaching. Partly due to his vigorous championing of younger composers and new styles, he was never successful in his attempts to gain a permanent teaching position for himself, though he was an examiner for many institutions (e.g. the Conservatoires of Brussels, Rheims and Marseilles). He was rejected for the post of Professor of counterpoint and fugue at the Paris Conservatoire in 1926 by 20 votes to two (the two being Albert Roussel and Maurice Emmanuel), but from 1935 to 1939 he was allowed to teach fugue and modal polyphony at the Schola Cantorum.

He visited the USA four times to lecture and teach in 1918-19, 1928, 1929 and 1937. On the second and third visits he taught at the University of California, Berkeley, through arrangements made by Catherine Urmer, who afterward lived with him until 1933.[2] On the 1929 visit his symphonic poem La Joie païenne won the Hollywood Bowl Prize for Composition and was performed there under the baton of Eugene Goossens. Even so, Koechlin had to pay for the preparation of orchestral parts, and in the 1930s he sank most of his savings into organizing performances of some of his orchestral works. In the 1940s, however, the music department of Belgian Radio took up his cause and broadcast several premieres of important scores including the first complete performance of the Jungle Book cycle. He died, and his body is buried, at his country home at Le Canadel, Var, aged 83. Some of his papers are housed at the University of California at Berkeley Library, donated by Catherine Urmer's husband Charles Rollins Shatto.