This comprehensive textbook titled "Fundamentals of Renewable Energy and Green Technologies" has been developed to meet the requirement of students and faculty of these disciplines besides other disciplines of science stream such as environmental sciences. The focus of the book is to cover various aspects of bioenergy and renewable clean technologies such as the solar, hydro including Oceans, and wind. The contents covered are as per the Dean's Committee recommendations for various disciplines. The book has been divided into sixteen chapters namely: Classification of energy sources, Biomass and briquetting, Combustion process, Principles of pyrolysis, Gasifiers, Biogas production processes, Biogas plants, Vegetable oils, Biofuels, Solar energy measurement and applications, Solar collectors and their applications, Solar dryers, Photovoltaic cells and practical applications, Hydropower, Wind energy and Life cycle cost analysis. The book is highly illustrated and written in simple and easy to understand English. Glossary of terms, theory and objective type questions and subject index has been included for the benefit of the students. The author believes that the book should prove to be a valuable textbook and an academic asset for students and staff of colleges and universities worldwide. Field practitioner may find it handy to refer the book while dealing with renewable energy in their day to day activities. The author envisages that this textbook will emerge as a valuable academic resource for students and staff alike across colleges and universities worldwide. Furthermore, practitioners in the field will find it indispensable for reference, aiding them in navigating the intricacies of renewable energy in their day-to-day activities.