This book provides a comprehensive exploration of piezoelectric polymers and composites, detailing their structures, fabrication, and applications across fields such as biomedical, electronic, and environmental science. Addressing the demands of Industry 4.0 and the Internet of Things, it delves into the most relevant materials like Polyvinylidene Fluoride and Poly-l-Lactic Acid, highlighting their properties, functionality, and versatility in energy harvesting, sensing, actuation, and biomedical applications, among others. Each chapter introduces fundamental concepts, recent advancements, and future directions, serving as both a reference for current knowledge and a guide for ongoing research in piezoelectric materials science.