Potassium cyanate is an inorganic compound with the formula KOCN (sometimes denoted KCNO). It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was 20,000 tons in 2006.

The cyanate anion is isoelectronic with carbon dioxide and with the azide anion, being linear. The C-N distance is 121 pm, about 5 pm longer than for cyanide. Potassium cyanate is isostructural with potassium azide.

The potassium and sodium salts can be used interchangeably for the majority of applications. Potassium cyanate is often preferred to the sodium salt, which is less soluble in water and less readily available in pure form.

Potassium cyanate is used as a basic raw material for various organic syntheses, including, urea derivatives, semicarbazides, carbamates and isocyanates. For example, it is used to prepare the drug hydroxyurea. It is also used for the heat treatment of metals (e.g., Ferritic nitrocarburizing).

Potassium cyanate was investigated as a treatment for sickle cell anemia, because it carbamylates the lysine and terminal amines in the deformed hemoglobin, modifying those areas' hydrophobicity. It has similarly been proposed to treat veterinary malaria.

Commercial KOCN is prepared by heating urea with potassium carbonate at 400 °C:

The reaction produces a liquid. Intermediates and impurities include biuret, cyanuric acid, and potassium allophanate (KO₂CNHC(O)NH₂), as well as unreacted starting urea, but these species are unstable at 400 °C.

Potassium cyanate is also formed by the oxidation of potassium cyanide, either with oxidizing agents or at high temperature in air.