There are many books designed for the introductory course in geotechnical engineering for undergraduate civil engineering students. The majority, if not all, of these textbooks focus on saturated soil mechanics. Unsaturated soil mechanics textbooks are catered towards graduate students and professionals. The most popular introductory soil mechanics textbooks put little emphasis on unsaturated soil mechanics. This book presents a new approach to teaching the subject, based on fundamentals of unsaturated soils, and extending the description of applications of soil mechanics to a wide variety of topics. Also included are a number of topics typically left out of undergraduate geotechnical courses such as Site Investigations, Yield and Plastic Behavior, Thermodynamics for Soil Problems, Slope Stability, Soil Dynamics, Erosion of Soil, Instrumentation. The soil mechanics textbook purchased by undergraduate students for their introductory geotechnical engineering course is often the only geotechnical engineering book purchased if the student does not pursue a graduate degree. This would be a comprehensive soil mechanics book that they could refer as they start and continue their career.