Louis de Broglie (1892-1987), Nobel laureate in physics, is a major figure in quantum physics. His work Théorie de la Quantification dans la Nouvelle Mécanique (Theory of Quantification in the New Mechanics) explores the principles of quantification (the fact that certain physical quantities can only take discrete values) within the framework of the new wave mechanics. This book is an important contribution to the development of quantum physics and its interpretation, at a time when the field was in full swing. It is a reference for the study of the foundations of modern quantum physics.