This book is a basic introduction to the subject of fluid mechanics and is intended for undergraduate and beginning graduate students of science and engineering. There is enough material in the book for at least two courses. No previous knowledge of the subject is assumed, and much of the text is suitable in a first course on the subject. On the other hand, a selection of the advanced topics could be used in a second course. I have not tried to indicate which sections should be considered advanced; the choice often depends on the teacher, the university, and the field of study. Particular effort has been made to make the presentation clear and accurate and at the same time easy enough for students. Mathematically rigorous approaches have been avoided in favor of the physically revealing ones.