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Storage carbohydrates, or storage polysaccharides, are polysaccharides used by organisms to store energy and carbon. In plants, the principal storage carbohydrate is starch, a mixture of amylose and amylopectin synthesized in plastids from glucose derived from photosynthesis. Starch is stored in seeds, roots, and tubers and can be mobilized when energy is needed. In animals, glycogen serves as the main short‑term storage form of glucose, predominantly found in liver and muscle tissues, with a highly branched structure that allows rapid release of glucose.

Both starch and glycogen are polymers of glucose linked by α(1→4) glycosidic bonds, with α(1→6) branching in glycogen and, to a lesser extent, in amylopectin. Their degradation yields glucose or maltose during energy demand. The enzymes involved include starch and glycogen phosphorylases, debranching enzymes, and various hydrolases that cleave internal bonds.

In human nutrition, starch is a major dietary carbohydrate. The digestibility and glycemic response depend on the amylose-to-amylopectin ratio and granule structure; resistant starch escapes digestion and acts as dietary fiber, contributing to gut health and slower energy release. Some microorganisms store energy as polyglucans, while trehalose serves as an important disaccharide storage and stress-protection molecule in certain insects and fungi. In algae, starch is also the common storage carbohydrate, though some species accumulate other polymers.

Starch and glycogen have broad applications in industry and daily life, including food production, fermentation processes, and the manufacture of bioplastics and pharmaceuticals, reflecting their central role as biological energy reserves.