This book provides a concise introduction to the physics of gravitational waves. It is aimed at graduate-level students and PhD scholars.Ever since the discovery of gravitational waves in 2016, gravitational wave astronomy has been adding to our understanding of the universe.Gravitational waves have been detected in the past few years from several transient events such as merging stellar-mass black holes, binary neutron stars, etc. These waves have frequencies in a band ranging from a few hundred hertz to around a kilohertz to which LIGO type instruments are sensitive. LISA will be sensitive...