This book is a basic introduction to the principles of circular particle accelerators and storage rings. Particle accelerators used to be the exclusive province of physicists exploring the structure of the most fundamental constituents of matter. The text presented here starts with a historical introduction to the field and an outline of the basic concepts of particle acceleration and phase focusing. It goes on to give more details of how the transverse and longitudinal motions of the particle beam can be analyzed, including treatments of lattice design, compensation schemes, transition crossing, and other radio frequency effects. Operational and diagnostic techniques and the optimization of luminosity are discussed in detail. One chapter is devoted to radiation and the special features of synchrotron light sources. Although the book emphasizes circular machines, much of the treatment applies equally to linear machines and transfer lines.