Erbium(III) nitrate is an inorganic compound, a salt of erbium and nitric acid with the chemical formula Er(NO<sub>3</sub>)<sub>3</sub>. The compound forms pink crystals, readily soluble in water. A pentahydrate and hexahydrate also exist.
Dissolving metallic erbium in nitric acid:
Dissolving erbium oxide or hydroxide in nitric acid:
Reaction of nitrogen dioxide with metallic erbium:
Both erbium(III) nitrate and its crystalline hydrate decompose on heating. The hydrated erbium nitrate thermally decomposes to form ErONO<sub>3</sub> and then erbium oxide.
It is used to obtain metallic erbium and is also used as a chemical reagent.