ReH3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Re3+ is bonded to twelve equivalent H1- atoms to form a mixture of corner and face-sharing ReH12 cuboctahedra. There are six shorter (1.93 Å) and six longer (2.20 Å) Re–H bond lengths. H1- is bonded in a distorted rectangular see-saw-like geometry to four equivalent Re3+ atoms.