This is a text on superconductivity, an area of intense research activity worldwide. The book is in three parts. The first covers the London, Pippard and GinzburgSHLandau theories, which are used to discuss a wide range of phenomena involving surface energies, vorticity, the intermediate and mixed states, boundaries and boundary conditions, the upper critical field in bulk, thin film and anisotropic superconductors, and surface superconductivity. The second part discusses the microscopic theory of Bardeen, Cooper and Schrieffer. The theory is used to discuss quasi particle tunneling and the Josephson effects from a microscopic point of view. The final part of the book treats nonuniform superconductors using the BogoliubovSHde Gennes approach with which it is possible to extract many important results without invoking Green's function methods. This text will be of great interest to graduate students taking courses in superconductivity, superfluidity, many body theory, and quantum liquids. It will also be of value to research workers in the field of superconductivity.