Sodium Tripolyphosphate (STPP) is an inorganic compound with formula Na5P3O10. It is the sodium salt of the polyphosphate penta-anion, which is the conjugate base of triphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, especially detergents. Environmental problems associated with eutrophication is attributed to its widespread use.

For detergent uses, the majority of Sodium Tripolyphosphate is consumed as a component of commercial detergents. It serves as a "builder", industrial jargon for a water softener. In hard water, detergents are deactivated.

For food applications uses, Sodium Tripolyphosphate is a preservative for seafood, meats, poultry, and animal feeds. It is common in food production as E number E451. In foods, Sodium Tripolyphosphate is used to retain moisture. Many governments regulate the quantities allowed in foods, as it can substantially increase the sale weight of seafood in particular.

Other uses include "ceramics, leather (as Synthetic Tanning Agent), anticaking, setting retarders, flame retardants, paper, anticorrosion pigments, textiles, rubber manufacture, fermentation, antifreeze.