Disodium hydrogen phosphate, also known as sodium hydrogen phosphate, has the chemical formula Na?HPO? and is one of the sodium salts derived from phosphoric acid. It is a white, hygroscopic powder that is soluble in water, and its aqueous solution is weakly alkaline.

Disodium hydrogen phosphate can be used to produce citric acid, water softeners, fabric weighting agents, flame retardants, and is employed in glazes, soldering fluxes, pharmaceuticals, pigments, the food industry, and the production of other phosphates. It serves as an industrial water treatment agent, dyeing and washing agent, quality improver, neutralizer, antibiotic culture medium, biochemical treatment agent, and food quality enhancer.