The crystal structure of HgMo(6)S(8), mercury(II) hexa-molybdenum octa-sulfide, is based on (Mo(6)S(8))S(6) cluster units ( symmetry) inter-connected through inter-unit Mo-S bonds. The Hg(2+) cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg(0.973 (3))Mo(6)S(8).