Sodium stannate, formally sodium hexahydroxostannate(IV), is the inorganic compound with the formula Na2[Sn(OH)6].

This colourless salt forms upon dissolving metallic tin or tin(IV) oxide in sodium hydroxide and is used as a stabiliser for hydrogen peroxide.

[2] In older literature, stannates are sometimes represented as having the simple oxyanion SnO32−,[3] in which case this compound is sometimes named as sodium stannate–3–water and represented as Na2SnO3·3H2O, a hydrate with three waters of crystallisation.

[1] The anhydrous form of sodium stannate, Na2SnO3, is recognised as a distinct compound with its own CAS Registry Number,[4] 12058-66-1 , and a distinct material safety data sheet.

[5] Alkali metal stannate compounds are prepared by dissolving elemental tin in a suitable metal hydroxide, in the case of sodium stannate by the reaction:[6] A similar reaction occurs when tin dioxide is dissolved in base: The anhydrous form can also be prepared from tin dioxide by roasting with sodium carbonate in a mixed carbon monoxide / carbon dioxide environment:[7] The anion is a coordination complex that is octahedral in shape, similar to most stannates, such as the hexachlorostannate anion [SnCl6]2−.