This book deals with the statistical theory of strongly coupled Coulomb systems. After an elementary introduction to the physics of nonideal plasmas, a presentation of the method of (nonequilibrium) Green's functions is given. On this basis, the dielectric, thermodynamic, transport, and relaxation properties are discussed systematically. Especially, the behavior of bound states in the surrounding plasma (lowering of the ionization energy), the ionization kinetics, and the equation of state of dense partially ionized hydrogen are each carefully investigated. Furthermore, generalized kinetic equations are derived which are also valid for short time scales. They are applied to ultra-fast processes and to plasmas in laser fields.