This book describes the phenomenon of plasma relaxation from the viewpoint of resistive magnetohydrodynamic theory. Magnetized plasmas relax when they seek their natural state of lowest energy subject to certain topological constraints imposed by the magnetic field. Relaxation occurs throughout the universe and may describe such diverse phenomena as dynamos, solar flares, and plasma magnetic confinement in fusion energy experiments. This book concentrates on the dynamic, rather than variational, aspects of relaxation. While the processes described are general, the book focuses on the Reversed Field Pinch experiment as a paradigm for plasma relaxation and dynamo action.