The goal of the DEF19 project is to fill a gap in the history of publishing, by developing a Dictionary of 19th-Century French Publishers. Such a tool does not exist yet – for this period (unlike for the 16th-18th centuries), and for this country (unlike other ones, such as Italy or Austria). All these works have proved to be immensely useful. Our aim will therefore be to create a dictionary which is both traditional and innovative. Traditional, in the form of a printed book, since publishing specialists and practitioners tend to prefer classical supports for reading and information. But also innovative, with an online crowdsourcing database, as well as a research blog designed as tools allowing exchange with the academic community. This project brings together various complementary skills : early-career researchers as well as seasoned scholars on the history of the book and publishing, organised around a team from the universities of Versailles Saint-Quentin-en-Yvelines (UVSQ) and Paris-Ouest-Nanterre-La Défense (UPOND), especially the Centre d’Histoire Culturelle des Sociétés Contemporaines (CHCSC), working with professionals of documentation, library and archives who could contribute their collections (from the Bibliothèque nationale de France, the French National Archives and the CHCSC), their daily practices and their expertise in the field of dictionaries, directories and databases to the creation of this project. Several scientific events will mark this four-year project, to develop the necessary rigorous methodological framework for data collection as well as for database and dictionary creation and edition. These events will allow us to bring forth the new opportunities for research that will emerge from an exhaustive investigation of an as yet incompletely explored field. As a dictionary, the DEF19 project will be a biographical work, but also a matter of prosopography, which could improve our knowledge of 19th-Century social, economic and cultural history: especially our modern cultural system based on mass culture and on the so-called “civilisation de l’imprimé” (civilisation of the printed word), in which the role of publishers has been and still is essential.