In the title coordination polymer, {[Ce2(C8H4O5)3(H2O)9]·6H2O} n , the asymmetric unit is formed by two Ce(III) atoms, three 5-hy-droxy-benzene-1,3-di-carboxyl-ate ligands, nine coordinating water mol-ecules and six water mol-ecules of crystallization. The two Ce(III) atoms are bridged by 5-hy-droxy-benzene-1,3-di-carboxyl-ate ligands acting in a bis-bidentate coordination mode, generating infinite chains along [101]. Both independent metal atoms are nine-coordinated, one by four O atoms from the carboxyl-ate groups of two bridging 5-hy-droxy-benzene-1,3-di-carboxyl-ate ligands and five O atoms from water mol-ecules, generating a tricapped trigonal-prismatic geometry. The coordination around the second Ce(III) atom is similar, except that one of the water mol-ecules is replaced by an O atom from an additional 5-hy-droxy-benzene-1,3-di-carboxyl-ate ligand acting in a monodentate coordination mode and forming a capped square-anti-prismatic geometry.