Doesburg, Theo van (1883-1931), Dutch painter, who was a leading advocate of the 20th-century neoplasticism movement in the Netherlands. He was one of the founders (1917) of De Stijl magazine, which promoted the neoplastic ideals of radical simplification based on the use of straight lines, right angles, and flat planes. Through speeches and articles, Doesburg spread neoplastic ideas to the Bauhaus school, where they influenced the course of mid-century architecture.