Plant-based biopolymers have gained significant research attention as sustainable and multifunctional materials for pharmaceutical applications. Commonly used biopolymers such as cellulose, starch, pectin, guar gum, and lignin have inherent properties of biocompatibility, biodegradability, non-toxicity, and tunable physicochemical properties. These properties, however, exhibit significant variability depending on the botanical source, extraction methodology, purity, and molecular structure. Recent developments in extraction techniques, chemical modifications, and nanostructuring techniques have enabled the development of advanced biopolymer systems for use in both conventional excipient roles, such as binders, fillers, disintegrants, coatings and in more advanced drug delivery systems, including controlled-release hydrogels, mucoadhesive carriers, and 3D-printed formulations. Plant-derived biopolymers are also promising in tissue engineering, wound healing, and biosensing applications. Despite challenges related to scalability and material variability, they can be considered sustainable and multifunctional biomaterials for the next generation of pharmaceutical applications. This chapter offers a comprehensive analysis of plant-derived biopolymers, discussing origin, structure, functional roles, and modification methods in the context of many pharmaceutical applications.