Reset control is concerned with how to reset a system when it is disturbed to overcome the inherent limitations of linear feedback control and to improve robustness. It has found applications in many practical systems including flexible mechanical systems, tapespeed control systems and high precision positioning systems. This book provides an introduction to the theory of reset control, and draws on the authors' own research and others' to explore the application of reset control in a variety of settings, with an emphasis on hard disk drive servo systems. Topics covered include the motivation and basic concepts of reset control systems; derivation of the describing function of reset systems; how the reset matrix affects the frequency domain property of a system; recent developments on stability analysis of reset control systems; robust stability of reset control systems with uncertainties; reset control systems with discrete-time reset conditions; optimal reset control design under fixed reset time instants; and reset control systems with conic jump sets. This book is essential reading for researchers, postgraduates and advanced students in control theory, and for research-based engineers who are interested in the theory of hybrid control systems and their engineering applications.