This book is aimed at researchers, materials scientists, and polymer engineers interested in sustainable materials. It focuses on the design, fabrication, and application of polyhydroxyurethane (PHU) polymers with an emphasis on environmental responsibility. PHUs represent a promising alternative to conventional isocyanate-based polyurethanes due to their lower toxicity and reduced environmental impact. Traditional polyurethanes rely on hazardous isocyanates, which pose risks to both human health and ecosystems. A key challenge lies in developing PHU systems that deliver strong performance, can be produced at scale, and meet the mechanical and thermal requirements of advanced applications. This work explores how innovative polymer design can balance sustainability with practical functionality, addressing the need for safer, high-performance materials in modern industry.