Potassium hypomanganate is the inorganic compound with the formula K3MnO4.

Also known as potassium manganate(V), this bright blue solid is a rare example of a salt with the hypomanganate or manganate(V) anion, where the manganese atom is in the +5 oxidation state.

It is an intermediate in the production of potassium permanganate and the industrially most important Mn(V) compound.

The resulting hypomanganate further reacts with water to produce manganate.

[2] A solution of potassium hypomanganate is produced: The compound is unstable due to the tendency of the hypomanganate anion to disproportionate in all but the most alkaline solutions.