This book introduces the basic concepts of environmental fluid dynamics. It is intended for use by students, researchers, engineers, and specialists working not only in general fluid research but also in the atmospheric and oceanic research fields. The Earth is covered by atmosphere and oceans and is exposed to solar wind. Therefore, the knowledge of fluid dynamics is essential for tackling its environmental issues. Although many textbooks have treated fluid dynamics, practically no book has been published that clearly describes all essential ideas, from the fundamentals of fluid dynamics to advanced environmental sciences, with careful sequential explanations of the governing mathematics. This book has been developed to solve these educational problems and has actually been in use in lectures in the graduate school of Kyushu University for more than 15 years.