BaS2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ba2+ is bonded to eight equivalent S1- atoms to form a mixture of corner and edge-sharing BaS8 hexagonal bipyramids. There are a spread of Ba–S bond distances ranging from 3.18–3.29 Å. S1- is bonded in a 5-coordinate geometry to four equivalent Ba2+ and one S1- atom. The S–S bond length is 2.12 Å.