A z-pinch is a deceptively simple plasma configuration in which a longitudinal current produces a magnetic field that tends to confine the plasma. The simple geometry and low cost made it an early candidate for controlled fusion experiments. However, instabilities and rapid plasma loss motivated the development of more complicated plasma confinement systems such as tokamaks and stellarators. Recent experiments, in which z-pinches produced unprecedented levels of radiation and power, have led to renewed interest in the configuration. As a result, z-pinch research is currently one of the fastest growing areas of plasma physics, with revived interest in z-pinch controlled fusion reactors along with investigations of new z-pinch applications, such as, very high power x-ray sources, high-energy neutrons sources, and ultra-high magnetic fields generators. This book provides a comprehensive review of the physics of dense z-pinches. Although the thrust of the treatment is theoretical, the authors also discuss recent experimental results as well as the operating systems of the main types of electrical drivers.