Résumé : This doctoral dissertation is an intellectual biography which discusses the projects and utopian visions of Paul Otlet (1868-1944). Paul Otlet formulated the concept of ‘documentation’, a field incorporating both study and practice that evolved out of bibliography before developing into information science. He was also a sociologist, an internationalist and indefatigable promoter of his conception of ‘universalism’ or ‘mondialism’, and of the Mundaneum and the Cité Mondiale. The major source that is used to throw new light on Otlet as a utopian thinker is an impressive collection of thousands of unpublished schemas. By means of an historical analysis of his schemas and writings, this thesis aims to identify the fundamental universalistic character of his utopian vision of knowledge organization and international organization. Universalism was a phenomenon incorporating complex personal ideals and social objectives, assuming different meanings in the fields of science, culture and politics, and reflecting the historical circumstances and undertakings of the time. By exploring how Paul Otlet and others dealt with the issue, this dissertation aims to contribute to the history of the idea of ‘universalism’.