磷酸二氢钾（化学式：KH₂PO₄）又称 磷酸一钾：

无色四方晶系结晶或白色结晶粉末，有潮解性，溶于水，不溶于乙醇，低毒性，健康危害等级1。水溶液有酸性，1%磷酸二氢钾溶液的pH为4.6。加热到400°C时熔化为透明状的液体，冷却后固化为不透明玻璃状的偏磷酸钾。

Monopotassium phosphate, MKP, (also potassium dihydrogen phosphate, KDP, or monobasic potassium phosphate), KH₂PO₄, is a soluble salt of potassium and the dihydrogen phosphate ion 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.