In inorganic nomenclature, a manganate is any negatively charged molecular entity with manganese as the central atom.However, the name is usually used to refer to the tetraoxidomanganate(2−) anion, MnO2−4, also known as manganate(VI) because it contains manganese in the +6 oxidation state.Manganates are the only known manganese(VI) compounds.

Other manganates include hypomanganate or manganate(V), MnO3−4, permanganate or manganate(VII), MnO−4, and the dimanganate or dimanganate(III) Mn2O6−6.A manganate(IV) anion MnO4−4 has been prepared by radiolysis of dilute solutions of permanganate. It is mononuclear in dilute solution, and shows a strong absorption in the ultraviolet and a weaker absorption at 650 nm.