Erbium(III) acetate is the acetate salt of erbium, with the proposed chemical formula of Er(CH3COO)3.

It can be used to synthesize some optical materials.

[2] The tetrahydrate of erbium(III) acetate is thermally decomposed at 90 °C, giving a proposed anhydride: Continued heating to 310 °C will form ketene: At 350 °C, the proposed Er(OH)(CH3COO)2 loses acetic acid to yield a material of the formula ErOCH3COO, forming Er2O2CO3 at 390 °C, finally obtaining Er2O3 at 590 °C.

[3]