This book provides a comprehensive coverage of the theory and principle of the Hoek-Brown (HB) failure criterion, methods or guidelines for estimating the HB input parameters, and the methodology of application of the HB criterion in rock engineering projects. It aims to help researchers, engineers and research students who work in the area of rock mechanics and mining engineering. Academics can quickly obtain an overview of the state of the art of the theory and principle of the Hoek-Brown criterion by reading the book before they advance their researches on the topics related to rock failure criteria. Geotechnical engineers can select appropriate Hoek-Brown input parameters for the design and analysis of rock engineering projects with the help of the principles introduced in this book. Research students may use the book as a textbook to learn the principle of rock mechanics related to rock mass properties.