Potassium hydroxide is an inorganic compound with the formula KOH and is commonly called caustic potash. Along with sodium hydroxide, this colourless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its re-activity toward acids and its corrosive nature.

It is also used as an alkaline builder in soap and detergent formulations, in liquid fertilizers that require a highly soluble potassium nutrient value and in the manufacturing of potassium compounds.