Due to their efficient mechanical properties, light weight, and low noise during operation, plastic gears are replacing metallic gears in traditional and new applications. However, due to a lack of material characterization and complex relations between different geometric and operating parameters, polymer gear design remains an open challenge. This book serves as a comprehensive and professional guide on polymer gears design and processing. It will provide the reader with current developments carried out in the field of plastic gears production, characterization, and applications. This will include material development, tribological properties, simulations, and processing methods.