This book covers the essential theories of thermodynamics supported by a large number of solved examples to enhance the vision of the students towards application of thermodynamics in engineering practice. In this book, the author has addressed the subtleties of the subject matter where students feel uncomfortable, drawing on his more than two decades of experience of teaching at undergraduate and postgraduate levels. The book has evolved from class lecture notes prepared over the years, while teaching the subject and therefore presents the subject in a coherent and logical manner, covering all the nuance of the subject. The whole book is divided into nine chapters, which covers all the fundamental concepts of Zeroth, First and Second Laws of Thermodynamics, Thermodynamic relations, the concept of Availability, Exergy and vapour, Gas power cycles, and Thermodynamic potential. The book is written in simple and lucid language and shall meet the requirements of undergraduate students of engineering and technology studying in various institutes/universities across the globe.