Sodium bisulphate, also known as sodium hydrogen sulphate is the sodium salt of the bisulphate anion, with the molecular formula NaHSO4. Sodium bisulphate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium base, typically either in the form of sodium hydroxide or sodium chloride. It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic.

Sodium bisulphate is used primarily to lower pH. For technical-grade applications, it is used in metal finishing, cleaning products and to lower the pH of water for effective chlorination in swimming pools and hot tubs.