Antimony triselenide is the chemical compound with the formula Sb₂Se₃. The material exists as the sulfosalt mineral antimonselite, which crystallizes in an orthorhombic space group. In this compound, antimony is assigned the oxidation state 3+ and selenium 2-, but in fact the bonding in this compound is highly covalent as reflected by the black color and semiconducting properties of this and related materials.