A major barrier to the introduction of ferroelectric devices into mass markets remains their limited reliability due to fatigue. The underlying physical and chemical mechanisms of this material fatigue phenomenon are extremely complex, and the relevant influences range from single-point defects to macroscopic boundary conditions. This book summarizes the different aspects of fatigue in ferroelectrics. It is primarily concerned with bulk material effects. Mechanical, electrical, and physico-chemical processes are described; reference data are given for different loading regimes and boundary conditions; and various fatigue models are compared. The monograph also demonstrates how the results of acoustic emission and of microscopy studies reveal the microscopic origins of fatigue in ferroelectric devices.