Constant Anton Nieuwenhuys (21 July 1920 – 1 August 2005) was a Dutch painter, and one of the foremost innovators of Unitary Urbanism. In 1941, he became deeply interested in the work of Paul Cézanne, Cubism and German Expressionism. He was born in Amsterdam. Generally known simply as Constant, in 1948 he founded the Experimentele Groep in Holland with Corneille, Karel Appel and his own brother, Jan Nieuwenhuys. They then went on to link up with Christian Dotremont and Joseph Noiret of Belgium and Asger Jorn of Denmark to form CoBrA. In 1958 he helped form the Situationist International where he is most noted for his contribution to unitary urbanism