The late William R. Sears (1913-2002) studied at the California Institute of Technology under the renowned engineer and physicist Theodore von Karman. During World War II Sears served as chief of aerodynamics and flight testing for Northrop Aircraft Corporation where he worked on projects including the P-61 Black Widow and Northrop’s Flying WingA . In 1946 he became director of the newly created Graduate School of Aeronautical Engineering of Cornell University in Ithaca, New York. In 1974 Sears joined the Department of Aerospace and Mechanical Engineering of the University of Arizona. Introduction to Theoretical Hydrodynamics was originally prepared by William Sears in 1948 for use in classes at Cornell University. Revised periodically during the ensuing decades it has remained a popular text, the value of which is recognized throughout the field even today. Formally published for the first time, this edition features updates prepared by former students of Sears to enhance ease of use by today’s students. These include the presentation of Sample Problems and their solutions throughout the text.The book also features Exercises whose solutions are provided in the accompanying Solutions Manual.