The nature of the symmetry changes associated with phase transitions in stibnite, Sb2S3, has been investigated by powder and single crystal X-ray diffraction. Above 420 K stibnite (I) is centrosymmetric Pbnm. Stibnite (II) is stable between 290 and 420 K and is acentric P21nm. Below 290 K stibnite (III) is stable and systematic absences indicates that this phase is monoclinic with space group P21 or Pm, or triclinic P1, but the cell dimensions remain geometrically orthorhombic. These findings are in agreement with variations in physical and electrical properties reported in the literature.