This chapter provides a comprehensive review of natural polysaccharides, their sources, characteristics, properties, and applications in food and pharmaceutical industries. Natural polysaccharides, such as cellulose, starch, chitin, and chitosan, are renewable and biocompatible, making them valuable in various applications. They are used in drug delivery systems due to their biodegradability, biocompatibility, and bioactivity. The chapter discusses the processing and characterization of natural polymers, including extrusion molding, solvent casting, and the use of nanocellulose. It also covers the extraction, purification, and modification of cellulose and starch, highlighting their potential in bioplastics and composites. The biological applications of natural polymers, such as anti-inflammatory, hypoglycemic, hypocholesterolemic, anticoagulant, and antiviral activities, are explored. Additionally, the chapter examines the use of natural polymers in food as stabilizers, thickeners, and emulsifiers, and their regulatory aspects in the food industry. Finally, it discusses the pharmaceutical applications of natural polymers, particularly in transdermal drug delivery systems, emphasizing their advantages over synthetic polymers.This chapter provides a comprehensive review of natural polysaccharides, their sources, characteristics, properties, and applications in food and pharmaceutical industries. Natural polysaccharides, such as cellulose, starch, chitin, and chitosan, are renewable and biocompatible, making them valuable in various applications. They are used in drug delivery systems due to their biodegradability, biocompatibility, and bioactivity. The chapter discusses the processing and characterization of natural polymers, including extrusion molding, solvent casting, and the use of nanocellulose. It also covers the extraction, purification, and modification of cellulose and starch, highlighting their potential in bioplastics and composites. The biological applications of natural polymers, such as anti-inflammatory, hypoglycemic, hypocholesterolemic, anticoagulant, and antiviral activities, are explored. Additionally, the chapter examines the use of natural polymers in food as stabilizers, thickeners, and emulsifiers, and their regulatory aspects in the food industry. Finally, it discusses the pharmaceutical applications of natural polymers, particularly in transdermal drug delivery systems, emphasizing their advantages over synthetic polymers.