Thulium(III) oxalate is the oxalate of thulium with the chemical formula Tm2(C2O4)3.

Its hydrate can be prepared by reacting an aqueous solution of thulium(III) chloride and a benzene solution of dimethyl oxalate.

[2] Its pentahydrate is decomposed by heat to obtain the dihydrate, which is further heated to obtain thulium(III) oxide.

[3] It reacts with hydrochloric acid to obtain H[Tm(C2O4)2]·6H2O.

[4]