"The Primordial Universe - L'univers primordial" is a specialized book that thoroughly examines the connection between cosmology and particle physics over the last decade. It provides a comprehensive introduction to the concepts of supersymmetry, superstring theory, and M-theory, responding to the growing interest in evaluating the cosmological implications of these theories. The book is based on a series of advanced courses that address the physics of the very early universe and take into account the latest advancements in understanding fundamental interactions. It covers both classical topics such as inflation, primordial fluctuations, dark matter, and baryogenesis, as well as the latest ideas regarding the events at and before the Big Bang. This extensive analysis makes the book a valuable resource for students and professionals who wish to engage with the fundamental questions of cosmology and particle physics.