X-ray binaries are stellar systems that combine one normal star (like our sun) and a smaller star, such as a white dwarf, a neutron star, or a black hole. This timely text provides a comprehensive overview of the unique and varied behavior of these combinations. Fifteen specially-written chapters by a team of the world's foremost researchers in the field explore all aspects of the X-ray binaries, including the X-ray, ultraviolet, optical, and radio properties of these violent systems, and address key issues such as how these systems formed and what their fate might be. They also discuss X-ray bursts and quasi-periodic oscillations, the connections between millisecond radio pulsars and low-mass X-ray binaries, and how the magnetic field of a neutron star decays. This long-awaited review provides graduate students and researchers with the standard reference on X-ray binaries for many years to come.