In chemistry, tetrahydroxozincate or tetrahydroxidozincate[1] is a divalent anion (negative ion) with formula Zn(OH)2−4, with a central zinc atom in the +2 or (II) valence state coordinated to four hydroxide groups.

These names are also used for the salts containing that anion, such as sodium zincate Na2Zn(OH)4 [2] and calcium zincate CaZn(OH)4·2H2O [3] Zincate salts can be obtained by reaction of zinc oxide (ZnO) or zinc hydroxide (Zn(OH)2) and a strong base like sodium hydroxide.

It is now generally accepted that the resulting solutions contain the tetrahydroxozincate ion.

[4] Earlier Raman studies had been interpreted as indicating the existence of linear ZnO2−2 ions.

[5] The name "zincate" may also refer to a polymeric anion with formula approaching [Zn(OH)−3]n, which forms salts such as NaZn(OH)3·H2O,[6] or to mixed oxides of zinc and less electronegative elements, such as Na2ZnO2.