As per the directions from The Supreme Court of India, UGC has made mandatory a course of Environmental Science for undergraduate students in Indian universities. This book has been written to cater the needs of B.E./B.Tech students according to the new syllabus prescribed by Gujarat Technical University. This book comprises of five units which covers the entire syllabus. Topics like principles of environmental science, environmental pollution, social issues like acid rain, global warming, etc are included. New developments like Green buildings and smart cities are also included. This book has been written in a simple and lucid manner. Most of these topics are traditionally taught in environmental science and engineering in several universities and institutes. Hence this book will be useful for other universities as well. Figures and tables are incorporated wherever necessary to make the concept clearer. This book also contains short questions with answers and review questions. Case studies on various environmental issues have been included. Author hopes that this book will be useful for both students and faculty alike.