Promethium(III) oxalate is an oxalate of promethium, with the chemical formula Pm2(C2O4)3.

Its decahydrate crystallizes in the monoclinic crystal system with space group P21/m.

[1] Promethium(III) oxalate trihydrate can decompose into stable basic carbonate Pm2O2CO3,[2] and generate promethium(III) oxide at higher temperatures.

[3] In all lanthanide oxalates, promethium(III) oxalate has the lowest solubility.

[4]