Michel Jouvet (1925–2017) is one of the most important figures in the contemporary history of the neuroscience of sleep and dreams, and one of the most awarded French researchers of the last century. Yet this former CNRS gold medalist and winner of the Cino Del Duca World Prize remains little known—not to say unknown—outside the field of sleep medicine, especially in non-French-speaking countries, where the name of his American counterpart, William C. Dement, is more familiar. Often reduced to his experiments on cats and the discovery of what he called “paradoxical sleep,” Jouvet left behind a rather unique body of work that includes not only countless publications on sleep and dreams—neurophysiological as well as ethnological and psychological—but also major contributions to clinical medicine, two novels and an impressive collection of personal dream accounts and drawings, which now make it possible to explore the nocturnal side of the last 50 years of his life. This article draws on unpublished archives to illuminate all these little-known and unknown aspects of Jouvet's life and work, highlighting his hidden links with 19th-century scientific oneirology and bringing to light its paradoxes.