The crystal structure of a new mineral of the stibnite group, Sb₂Se₃, has been determined. The cell constants, obtained by least-squares calculation from direct θ-value’s measurements on the diffractometer are: a=1.158 8(5),b= 1.1744(4),c = 0.395 5(2) nm; orthorhombic;V = 0.538 23 nm³; Z = 4. The space group isPbnm. X-ray single crystal data, using MoKα radiation, were measured on a RIGAKU RASA-5RP automated diffractometer and refined to a finalR index of 0.048 1. Sb₂Se₃ is isostructural with Sb₂S₃ and Bi₂S₃. Each Sb(1) atom is six-coordinated by 3 Se(1), 1 Se(2) and 2 Se(3) atoms at distances 0.266 0–0.323 6 nm. Each Sb(2) atom is seven-coordinated by 2 Se(1), 2 Se(2) and 3 Se(3) atoms at distances of 0.258 1–0.346 7 nm. The crystal structure consists of chains parallel toc or needle axis. The strongest bonds (shortest separations) are within the chains. Many important physical properties of antimonselite (optical, ferroelectric, etc.) are related to its crystal structure.