This is a three-part text on the subject of superconductivity, an area of intense research activity worldwide. The first part covers the London, Pippard and Ginzburg-Landau 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 section discusses the microscopic theory of Bardeen, Cooper and Schreiffer. 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 non-uniform superconductors using the Bogoliubov-de 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 and research workers in the fields of superconductivity, superfluidity, many body theory, and quantum liquids.