Potassium sulphate (K2SO4) is a non-flammable white crystalline salt which is soluble in water. The chemical compound is commonly used in fertilizers, providing both potassium and sulphur.

The dominant use of potassium sulphate is as a fertilizer. It does not contain chloride, which can be harmful to some crops. The crude salt is also used occasionally in the manufacture of glass. Potassium sulphate is also used as a flash reducer in artillery propellant charges. It reduces muzzle flash, flareback and blast overpressure.