French art dealer, collector, and publisher. He opened his first gallery in 1914 with an exhibition of Mikhail Larionov and Natalia Goncharova. He later showed Derain, Matisse, and Picasso. He was far more flamboyant in the marketing of modern art than were Vollard and Kahnweiler. Apollinaire helped publicize his activities in his articles and Guillaume published a review, Les Arts à Paris (1918–35), which promoted his gallery's artists. (The final issue was edited posthumously by his wife.) Albert Barnes was both an important client and a contributor to the publication. The two men shared an admiration for African and Oceanic art and articles on these were a regular feature of the review. Guillaume's collection is now on view at the Musée de l'Orangerie in Paris.
From A Dictionary of Modern and Contemporary Art in Oxford Reference.