Julianus Marie August de Boeck (Merchtem, Belgium, May 9, 1865 – Merchtem, October 9, 1937) was a Flemish composer, organist and music pedagogue.
From 1880 he studied organ at the Royal Conservatory of Brussels under Alphonse Mailly, whose assistant he became until 1902. In 1889 he met the young Paul Gilson who became a close friend and, despite being the same age, his teacher for orchestration. Gilson encouraged de Boeck's composition work.
He became an organist at various churches in Belgian villages (1892-1894 in Merchtem, 1894-1920 in Elsene). His academic career continued in 1907 as professor of harmony at the Royal Conservatory of Antwerp (1909–1920) and the Brussels Conservatory, and as director of the Conservatory of Mechelen (1921–1930). In 1930 August de Boeck retired to his birthplace, Merchtem.
As with Gilson, his style was influenced by the Russian Five, and especially Rimsky-Korsakov. Along with Gilson, he introduced impressionist composition in Belgium.