Nanotechnology deals with designing, processing, and fabrication of nanostructures and nanomaterials that have highly diverse applications. It also includes a fundamental understanding of the phenomena of nanomaterials and nanostructures. This chapter covers the extensive research on the processing, structure, and properties of biopolymers, bionanocomposites, and bionanomaterials. It provides the work based on the different bio‐based polymers and their nanostructures. Cellulose, chitin/chitosan, starch, soy protein isolates, casein, alginates, and other biopolymers when downscaled to nanosize, can be applied in the field of biology, medicine, optics, mechanical, electronics, and so on. Bionanoconjugates provide a rational perspective due to their unique properties such as size, shape, surface charge, and physico‐chemical properties with extraordinary functionalities. The chapter discusses different biopolymers such as cellulose, chitin, starch, soy protein, casein, alginates, and others as well as their nanostructures, properties, characterization, and applications.