Potassium dimanganate(III), K<sub>6</sub>Mn<sub>2</sub>O<sub>6</sub>, is a manganese(III) compound. Unlike lithium and sodium manganites, MMnO<sub>2</sub>, which are best described as mixed oxides, potassium dimanganite contains discrete Mn<sub>2</sub>O anions in the solid state. It rapidly hydrolyzes in air.
K<sub>6</sub>Mn<sub>2</sub>O<sub>6</sub> is prepared as ruby-red crystals by the reaction of excess potassium oxide with manganese(II) oxide in a sealed nickel bomb at 610 ðC for ten days. The Mn<sub>2</sub>O anion has an Al<sub>2</sub>Cl<sub>6</sub>-type structure.