This textbook provides a comprehensive introduction to the phenomenological theories of superconductivity. Much emphasis is placed on a thorough development of theoretical approaches to understand the basic properties of superconductors and their most important applications. The content ranges from an overview of important experimental properties to the detailed description of the London theory and the Ginzburg-Landau theory. Prominent effects like the Meissner effect, critical magnetic fields, formation of vortices and many other phenomena are theoretically explained in great detail.