Iron(III) selenite is an inorganic compound with the chemical formula Fe2(SeO3)3.

It exists anhydrous form and as various hydrates.

The heptahydrate is produced by the reaction of ferric chloride and selenous acid (or sodium selenite) at a pH of 1.05.

[4] The single crystal diffraction of the trihydrate shows that its structure consists of two independent FeO6 octahedrons and SeO32− with a tetrahedral geometry.

[1] The anhydrous salt decomposes into Fe2O3·2SeO2 at 534 °C, generates 4Fe2O3·SeO2 at 608 °C, and finally obtains Fe2O3 at 649 °C.