Sodium orthosilicate is the chemical compound with the molecular formula Na4SiO4.

It is one of the sodium silicates, specifically an orthosilicate, formally a salt of the unstable orthosilicic acid H4SiO4.

In laboratory settings, it was found to be more effective than sodium hydroxide for some types of oil.

[5] Sodium orthosilicate has been found to stabilize ferrate films as an anticorrosion treatment of iron and steel surfaces.

However, the mineral chesnokovite, chemically the related salt disodium dihydrogen orthosilicate [Na+]2[SiO2(OH)2−2] · 8H2O, was recently identified in the Kola Peninsula.