This chapter presents plant-based bioplastics and sustainable materials as possible alternatives to traditional (petroleum-based) plastics. With an emphasis on thermal, physical, and mechanical properties, it also explains the definitions, origins, classifications, and manufacturing processes of bioplastics derived from plant sources such as cellulose, starch, polyhydroxyalkanoates, and polylactic acid. Extrusion and moulding (injection and blow moulding) are described, including the raw polymer modification and processing methods. Applications for consumer goods, packaging, agriculture, and biomedicine are examined, along with their drawbacks. The chapter concludes by highlighting technological developments and the use of plant-based bioplastics in the circular economy as a viable approach for manufacturing sustainable, renewable, and environmentally friendly materials.