Chitosan, a natural polycationic linear polysaccharide derived from chitin, has gained significant attention for its potential biomedical and pharmaceutical applications due to its non-toxicity, low allergenicity, biocompatibility, and biodegradability. Despite its low solubility in neutral and alkaline solutions, chemical modifications have enhanced its functional properties, making it versatile for various applications. This review highlights recent research, trends, and prospects in chitosan, emphasizing its special applications in pharmaceuticals and biomedicine. Chitosan is produced from chitin, primarily sourced from crustacean shells, through chemical or enzymatic deacetylation. Its properties, such as degree of deacetylation and molecular weight, influence its solubility and functionality. Chitosan hydrogels, composed of cross-linked polymer chains with high hydrophilicity, are particularly useful in tissue engineering, drug delivery, wound healing, and water treatment. In tissue engineering, chitosan-based biomaterials provide mechanical and structural support for tissue repair, enhancing osteogenesis and vascularization. In drug delivery systems, chitosan facilitates controlled release of drugs through oral, nasal, and ocular routes, improving therapeutic efficiency and reducing side effects. Chitosan's antimicrobial, antifungal, antitumor, and antioxidant activities make it effective in wound healing, where it promotes cell proliferation and collagen deposition. Additionally, chitosan is highly efficient in water treatment, adsorbing pollutants like dyes, metals, and organic compounds. The review also discusses the challenges and advancements in chitosan's production, characterization, and applications, emphasizing the increasing interest and development in these areas.Chitosan, a natural polycationic linear polysaccharide derived from chitin, has gained significant attention for its potential biomedical and pharmaceutical applications due to its non-toxicity, low allergenicity, biocompatibility, and biodegradability. Despite its low solubility in neutral and alkaline solutions, chemical modifications have enhanced its functional properties, making it versatile for various applications. This review highlights recent research, trends, and prospects in chitosan, emphasizing its special applications in pharmaceuticals and biomedicine. Chitosan is produced from chitin, primarily sourced from crustacean shells, through chemical or enzymatic deacetylation. Its properties, such as degree of deacetylation and molecular weight, influence its solubility and functionality. Chitosan hydrogels, composed of cross-linked polymer chains with high hydrophilicity, are particularly useful in tissue engineering, drug delivery, wound healing, and water treatment. In tissue engineering, chitosan-based biomaterials provide mechanical and structural support for tissue repair, enhancing osteogenesis and vascularization. In drug delivery systems, chitosan facilitates controlled release of drugs through oral, nasal, and ocular routes, improving therapeutic efficiency and reducing side effects. Chitosan's antimicrobial, antifungal, antitumor, and antioxidant activities make it effective in wound healing, where it promotes cell proliferation and collagen deposition. Additionally, chitosan is highly efficient in water treatment, adsorbing pollutants like dyes, metals, and organic compounds. The review also discusses the challenges and advancements in chitosan's production, characterization, and applications, emphasizing the increasing interest and development in these areas.