This book provides a clear understanding of dielectric elastomer materials suited for soft electromechanical systems (EMS) for numerous engineering applications by establishing the relationship between various stimuli and response. It provides a comprehensive introduction to electroactive polymer (EAP), a dielectric elastomer belonging to the class of smart materials, which possesses viscoelastic behavior and in response to the external electric field generates mechanical deformation, and vice-versa. In addition, high-energy density, high-strain rate, and low-elastic modulus, etc., make EAP a suitable material for various EMS applications. Despite having a wide range of applications, its non-linearity, viscoelastic losses, leakage current, etc., make it challenging for researchers as well as manufacturers to use it as actuators, sensors, generators, and so on. This book addresses the issue of non-linearity in dielectric elastomers along with their response to electrical, mechanical, and electromechanical loads with various suitable material models. It provides a complete understanding of material performance, working principle, and design will provide scope for the design, development, and manufacturing of novel devices with different input and response in the field of actuators, sensors, and generators. It is expected that the book is helpful for researchers from mechanical, electrical, mechatronics, and various other branches to understand the modeling and application aspects of dielectric elastomers completely.