Suitable for both undergraduates and graduates, this textbook provides an up-to-date, accessible introduction to thermal physics. The material provides a comprehensive understanding of thermodynamics, statistical mechanics, and kinetic theory, and has been extensively tested in the classroom by the author who is an experienced teacher. This book begins with a clear review of fundamental ideas and goes on to construct a conceptual foundation of four linked elements: entropy and the Second Law, the canonical probability distribution, the partition function, and the chemical potential. This foundation is used throughout the book to help explain new topics and exciting recent developments such as Bose-Einstein condensation and critical phenomena. The highlighting of key equations, summaries of essential ideas, and an extensive set of problems of varying degrees of difficulty will allow readers to fully grasp both the basic and current aspects of the subject. A solutions manual is available for instructors. This book is an invaluable textbook for students in physics and astronomy.