Paul Gilson (Brussels, 15 June 1865 - Brussels, 3 April 1942) was a Belgian musician and composer.
Gilson was born in Brussels. In 1866, his family moved to Ruisbroek in the Belgian province of Brabant. There he studied theory with the organist and choir director Auguste Cantillon, and began writing works for orchestra and choir. His first official training came from 1887-1889 under François-Auguste Gevaert in composition and under Charles Duyck in harmony and counterpoint at the Brussels Conservatory, and in 1889, he was awarded the Belgian Prix de Rome for a cantata, Sinaï, which was very well received. As the winner of the prize he was able to spend time in Bayreuth (1892), Paris (1893–4) and Italy (1895).
A large orchestral work, La mer, which was first performed in Brussels on 20 March 1892, established Gilson as a national musical figure and also gave him success abroad, though not in Paris.
In 1899 he became professor of composition at the Brussels Conservatory; he won the same post at Antwerp in 1904 but quit both after becoming inspector of music education in 1909, a post he would keep until 1930. Although he was a very prolific composer, his output decreased after 1905, after which Gilson wrote increasingly about music, in theory, criticism, and composition.
In 1925, a group of Gilson's students who called themselves Les Synthétistes (including René Bernier, Francis de Bourguignon, Théo De Joncker, Marcel Poot, Maurice Schoemaker, Jules Strens and Robert Otlet) first formed, declaring allegiance to Gilson's ideas about music. Along with Poot and Schoemaker, he founded La revue belge musicale in 1924; he was the chief editor until it folded in 1939. He also wrote pamphlets for Belgian radio.