Daniël "Daan" de Clercq (21 August 1854 in Heerde – 15 December 1931 in Haarlem) was a Dutch socialist and activist.
He was the grandson of Willem de Clercq and grew up in Haarlem where he became good friends with Frederik van Eeden at the HBS high school there.[1] After continuing his education by studying technology in Delft and chemistry in Berlin he settled in Leiden, but in 1878 he returned to Haarlem to become the technical director of a paint factory there, where he lived the rest of his life. For this factory he introduced several labor reforms which he then tried to scale to the rest of Haarlem and later as a member of the socialist labor party, to the rest of the country.[1] His first act was to create a room for workers to eat their meals; a "schaftlokaal" or cafeteria. He next instituted health insurance and accident insurance for his employees along the lines of Bismarck's Health Insurance Bill of 1883 and Accident Insurance Bill of 1884. He expressed the need for secondary school for the future workers of his factory and wished to create a training school connected to his factory. These extra expenses were not popular with his employer however and de Clercq quit his job in 1890.[1] In 1891, he began the Haarlem society called De Ambachtsschool to unify various city efforts to start the first vocational school in Haarlem.[2] He also became a member of the Haarlem Debating society where he advocated his views on housing and education reform for the working class in Haarlem. In 1883 he joined the Amsterdam freethought society De Dageraad.
He propagated land nationalisation whereby he combined the "gardencity" ideas of Ebenezer Howard with the socialist ideas of Domela Nieuwenhuis who he knew through "De Dageraad". He believed that by nationalizing the land and creating freestanding homes for everyone, more workers would have more energy for society due to better health. These ideas were popular among workers and reformers alike. He organized meetings where the painter-reformer Herman Heijenbrock and the writer-reformer Frederik van Eeden could air their social ideas.[1] He became an activist for vegetarianism. In 1894 he joined the newly formed NVB, the Dutch Vegetarian Society (Dutch: Nederlandse Vegetariërsbond) and became editor of its magazine Vegetarische Bode in 1897. In 1898 he succeeded Felix Ortt as chairman of the group and remained chairman until 1907. He published numerous brochures and articles and was a popular guest speaker for reformist groups. He was also candidate of the SDAP (Dutch socialist party).[1][3]