Dark-green platy crystals of the new compound Pb31O22Br10Cl8 (1) have been obtained by rapid quenching of a lead oxide halide melt. The structure of 1 (triclinic, P1, a = 12.1192(7)angstrom, b = 16.2489(10) angstrom, c = 18.3007(11) angstrom, alpha = 93.104(2)degrees, beta = 95.809(2)degrees, gamma = 111.252(1)degrees, V = 3325.4(3) angstrom(3), Z = 2) can be viewed as incorporation of [PbX6](4-) halide units (X = Br, Cl) into the defect PbO matrix. The latter represents a two-dimensional [O22Pb30](16+) cationic layer of OPb4 tetrahedra that can be derived from the [OPb] tetrahedral layer observed in tetragonal PbO. The layer consists of 22 symmetrically inequivalent OPb4 tetrahedra and represents the topologically most complicated arrangement of tetrahedra known to date.