Monopotassium phosphate (also potassium dihydrogen phosphate, KDP, or monobasic potassium phosphate, MKP) -- KH2PO4 -- is a complete soluble inorganic salt which is used as a fertilizer, a food additive and a fungicide. It is a source of phosphorus and potassium. It is also a buffering agent. When used in fertilizer mixtures with urea and ammonium phosphates, it minimizes escape of ammonia by keeping the pH at a relatively low level.

Fertilizer grade MKP contains the equivalent of 52% P2O5 and 34% K2O, and is labeled 0-52-34. MKP is often used as a nutrient source in the greenhouse trade and in hydroponics.
It is one of the components of Gatorade (used as both an emulsifier and pH buffer) and is used as an additive in cigarettes.