We report on the MOCVD synthesis of Sb2Te3 nanowires that self-assemble in a novel metastable polymorph. The nanowires crystallize in a primitive trigonal lattice (P3̅m1 SG #164) with lattice parameters a = b = 0.422 nm, and c = 1.06 nm. The stability of the polymorph has been studied by first principle calculations: it has been demonstrated that the stabilization is due to the particular side-wall faceting, finding excellent agreement with the experimental observations.