This book contains recent advances on theory of mixtures in geo-mechanics. It presents all the necessary material that is published and scattered in different journals. The book presents both basic principles and advanced topics. It includes a chapter on comparison of theoretical and experimental results. The first part of the book deals with the historic reviews, hydro-mechanics of geo-materials, and the fundamental theory of mixtures. The second part of the book deals with the Coupling Theory, Numerical Simulations, and Applications in real structures. The third part of the book deals with advanced topics such as unsaturated soils and theory of mixtures for non geo-materials. The book can be used as a textbook for an advanced course on geo-mechanics and geotechnical engineering.