The first nine-atom deltahedral clusters of lead in the solid state are found in the Zintl-phase K4Pb9. The compound crystallizes in the monoclinic space group P2(1)/m, Z = 4, with a = 9.648(3) Angstrom, b = 13.243(5) Angstrom, c = 15.909(8) Angstrom, and beta = 103.24(4)degrees. The isolated Pb-9(4-) clusters are of two different geometries, a monocapped square antiprism and an elongated tricapped trigonal prism.