Theo van Doesburg (born Christian Emil Marie Küpper) (August 30, 1883 - March 7, 1931) was perhaps the main name in the forefront of de stijl movement, after Piet Mondrian. As Mondrian was not directly committed with the publicizing affairs concerning the movement, Doesburg assumed this task and moved to Weimar, Germany in 1922 decided to make a hard influence over Bauhaus principal, Walter Gropius, in order to spread de stijl's influence.

Although Gropius accepted a turn towards constructivism in 1923, he did not feel like Doesburg could be a Bauhaus master. Doesburg than installed himself near to Bauhaus buildings and started to attract school students interested in the new ideas of constructivism. Later on, Doesburg would split with his master, Mondrian, because of a divergence about the directions of the lines in the square scheme of de stijl paintings. Mondrian did never accept diagonals, whereas Doesburg insisted on the diagonal's dynamic aspects, and indeed featured it in many of his works. However, Mondrian accepted some concepts of diagonals, such as in Monrdian's Lozenge paintings, where the canvas was rotated 45 degrees, while still maintaining horizontal lines. This effect gave the impressions of lines extending beyond the canvas while maintaining the horizontal characteristic Mondrian stuck to.

Aside his design activities which even included architecture (Houses for artists, together with Georges Vantongerloo, the designs for the decoration of Café Aubette), Doesburg also kept a link with DADA poetry, publishing the magazine DADA Holland under the false name of I. K. Bonset. Together with Eli Lissitsky and Kurt Schwitters, Doesburg pioneered the efforts to an International of Arts in two congresses held in Düsseldorf and Weimar, still in 1922.

He died in France in the '30s, after another international effort under the group Cercle et carré.