This textbook, addressed primarily to physics and engineering students, is a comprehensive introduction to waves and oscillations, both mechanical and electromagnetic. Elementary aspects of matter waves are also considered. One objective is to illustrate the physics involved in the description and analysis of waves through a wide range of examples, from purely mechanical and purely electromagnetic to coupled electro-mechanical waves, such as plasma oscillations and hydromagnetic waves. In this process, the use of complex amplitudes in the mathematical analysis is illuminated and encouraged to make tractable a wider range of problems than is ordinarily considered in an introductory text. General concepts and wave phenomena such as wave energy and momentum, interference, diffraction, scattering, dispersion, and the Doppler effect are illustrated by numerous examples and demonstrations. Among the special topics covered are waves on periodic structures and in solids, wave guides, a detailed analysis of light scattering from thermal fluctuations of a liquid surface, and feedback instabilities. Important ideas and equations are displayed in boxes for easy reference, and there are numerous examples throughout the text and exercises at the end of every chapter. Undergraduates and graduates should find this an indispensable account of this central subject in science and engineering.