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 in Brussels under Alphonse Mailly from whom he became an assistant until 1902. In 1889 he met the young Paul Gilson who became his close friend, and, despite their same age, his teacher for orchestration and his motivator for composition.
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 harmony professor at the conservatory of Antwerp (1909–1920) and the conservatory of Brussels, and as director of the conservatory of Mechelen (1921–1930). In 1930 August de Boeck retired to his birthplace.
His style was, together with that of Paul Gilson, influenced by the Russian Five (especially Rimsky-Korsakov), and they introduced musical Impressionism into Belgium.