Xylo-oligosaccharides (XOS) are short-chain carbohydrates derived from the enzymatic hydrolysis of xylan in plant fibers. Structurally composed of β-1,4-linked xylose units, they feature a unique C5 sugar backbone that distinguishes them from other prebiotics based on C6 sugars. XOS resist digestion in the upper gastrointestinal tract and reach the colon intact, where they selectively promote beneficial bacteria such as Bifidobacteria and Lactobacilli. Known for their excellent solubility, thermal and acid stability, and clean taste, XOS are widely used in health-focused formulations. Clinical studies demonstrate multiple benefits, including improved digestive function, support for balanced microbiota, enhanced immune response, and positive effects on lipid and glucose metabolism—making XOS a high-value prebiotic ingredient across functional foods, supplements, and medical nutrition.