Roelof Paul Citroen (Berlin 1896 – 1983 Wassenaar) was a Dutch artist, teacher, art collector, stamp designer (1949), and co-founder of the Nieuwe Kunstschool in Amsterdam. His traditional and Jewish upbringing, emphasizing the Bildungs-ideal, had a lasting influence on him. At the age of fourteen, he left the gymnasium and enrolled in an art school, heavily influenced by expressionism at the time. Unfortunately, he discovered that abstract art did not suit him, leading to disillusionment, and he stopped painting and drawing. This would not be the last time.

Paul worked at Walden bookstore, which also traded in modern art. Here, he met many renowned artists, from whom he began to buy art himself. He built an interesting collection with works by Wassily Kandinsky, Alexej von Jawlensky, Paul Klee, and Oskar Kokoschka. He also wrote reflections on contemporary art, with his first article on Marc Chagall published in Der Sturm in 1917.

In the same year, he settled in the Netherlands to engage in the art trade. After World War I, he returned to Berlin and became involved with members of the anarchist Dada movement. Inspired by his Dada friends, he created his first collages and montages using newspaper clippings, photos, and postcards. In 1920, while in Amsterdam, he became the unofficial representative of the Dada movement in the Netherlands and a propagandist for the modern art of Der Sturm.

Paul always spoke very modestly about his photomontages, as he attached little importance to this "playfulness." In 1922, he continued his education at the Bauhaus in Weimar, with Itten as the inspiring guru, and Klee and Kandinsky as teachers. In 1923, he created his most famous photomontage: 'Metropolis,' which inspired director Fritz Lang to the film classic Metropolis. However, he left Weimar after only two years because the Bauhaus focused on the constructive rather than the expressive. Citroen had little interest in abstract art; he considered painting abstract enough. He concluded that he had nothing to add to modernism.

Between 1924 and 1928, he traveled through Europe as a fur and art dealer. In 1929, five years later, he returned to photography. In addition to his work as a portrait photographer, he continued to trade in modern art and write about art.

In 1933, he co-founded the Nieuwe Kunstschool in Amsterdam with Charles Roelofsz, modeled after the Bauhaus. The development of the artist was central to this very liberal school, which managed to survive until 1943 despite financial difficulties. During the war, Citroen went into hiding as a Jew in 's Graveland. Before and after the war, he also taught at the Hague Art Academy until 1960, alongside Willem Schrofer and, for example, Rein Draijer. He had a significant influence on the students who are now called the Nieuwe Haagse School. Jan Wolkers also praised his lessons and enthusiasm.

As a painter, Citroen is primarily a portraitist. "I must rely on people." The general public knew him through his live portraits during broadcasts by Willem Duys. He inspired Hermanus Berserik to his distinctive style. Citroen created large standing portraits of him and 11 other artists. Some of his work and art collection can now be found in the Hannema-de Stuers Fundatie collection in Heino. In around 1974, the province of Overijssel acquired over 2000 works from and via Citroen for the provincial house.