This book offers an extensive review of research on chitin and chitosan, focusing on the bioconversion of chitin-rich fishery by-products for the production of enzymes and bioactive compounds. It delves into the chemical modification of chitin and chitosan, examining their properties and diverse applications across nutraceuticals, pharmaceuticals, cosmeceuticals, tissue engineering, regenerative medicine, and clinical veterinary fields. The book highlights the potential of chitinous biomaterials due to their exceptional material properties and biological functionalities. Key features of the book include: (1) an in-depth examination of microbial reclamation of chitin-containing fishery by-products; (2) a comprehensive overview of the synthesis and application of chitin and chitosan derivatives; and (3) contributions from leading global researchers. This publication is indispensable for scientists in academia and industry focused on chitin and chitosan, as well as university students and engineers interested in the advancement of sustainable and eco-friendly biomaterials.