The 21 chapters in this book presents a comprehensive overview of flexible supercapacitors using engineering nanoarchitectures mediated by functional nanomaterials and polymers as electrodes, electrolytes, and separators, etc. for advanced energy applications. The various aspects of flexible supercapacitors, including capacitor electrochemistry, evaluating parameters, operating conditions, characterization techniques, different types of electrodes, electrolytes, and flexible substrates are covered. This is probably the first book of its type which systematically describes the recent developments and progress in flexible supercapacitor technology, and will be very helpful for generating new and innovative ideas in the field of energy storage material for wearable/flexible industry applications.