Electroactive polymer (EAP) materials with large displacement response are showing great potential. The ability to induce large actuation strains such as stretching, squeezing, and bending makes these resilient materials remarkably similar to biological muscles. This book describes the mechanics of natural muscles and how EAP actuators mimic their actions. It examines materials, EAP function at the molecular level, and methods for predicting polymer response to external electric fields. The text discusses the future of EAP in robotics, entertainment, and medicine, among other industries.