Oligosaccharides are short chains of monosaccharide residues joined by glycosidic linkages, typically containing between three and ten sugar units. They occur naturally in many plant-based foods such as legumes, onions, garlic, and chicory. In nutrition, they function as prebiotic fibers that resist digestion in the upper gastrointestinal tract and are selectively fermented by beneficial gut microbiota in the colon, leading to the production of short-chain fatty acids that support intestinal health. Examples include fructooligosaccharides (FOS), galactooligosaccharides (GOS), and xylooligosaccharides (XOS). They are used in functional foods for their sweetening properties with lower caloric content and their ability to improve texture and moisture retention. Due to their fermentation, excessive consumption may lead to gastrointestinal discomfort like bloating and gas in sensitive individuals. Chemically, they exhibit varying degrees of polymerization and branching, influencing their solubility and physiological effects.