Potassium bisulfate (potassium bisulphate) is an inorganic compound with the chemical formula KHSO4 and is the potassium acid salt of sulfuric acid.

More than 1 million tons were produced in 1985 as the initial stage in the Mannheim process for producing potassium sulfate.

[5] Potassium bisulfate is also used as a disintegrating agent in analytical chemistry or as a precursor to prepare potassium persulfate, a powerful oxidizing agent.

[6] Mercallite, the mineralogical form of potassium bisulfate, occurs very rarely.

[7] Misenite is another more complex form of potassium bisulfate with the formula K8H6(SO4)7.