potassium dioxide, K2O, is a white to yellow crystalline solid that is the simplest oxide of potassium. It is a caustic inorganic compound and a basic anhydride that reacts with strong acids, releasing hydrogen gas as a byproduct. It is used as a fertilizer, in manufacturing soap, and glass production. It also has a variety of medical uses, including the treatment of fungal granulomatous disease in livestock and infections associated with zygomycetes.

K2O is an ionic compound, because potassium has only one electron in its outermost shell and oxygen is short of two electrons to gain a fulfilled octet, so the atoms bond together forming ionic bonds. Two atoms of potassium and one atom of oxygen form a tetrahedron, and the molecule has a net positive valency.

The compound is made by reacting potassium hydroxide with water, in a process that is usually performed in an autoclave. It is also made by vaporizing an aqueous solution of potassium chloride with an electric current, in which case the chlorine escapes as a gaseous byproduct and potassium hydroxide forms.

In a study of the effect of potassium deficiency on the intracellular pH of skeletal muscle, Albino rats fed diets containing either 0.003% or 0.75% potassium for 40 days showed that the concentration of dissolved carbon dioxide and sodium in the sacrospinalis muscle of potassium-deficient animals was significantly less than that of the control rats. This led to a fall in the value of the intracellular pH for both ionized calcium and carbon dioxide in potassium-deficient muscles, whereas values for other ions were unaffected.