Arsenic trisulfide is the inorganic compound with the formula As₂S₃. It is a bright yellow solid that is insoluble in water. It also occurs as the mineral orpiment (Latin: auripigment), which has been used as a pigment. It is produced in the analysis of arsenic compounds. It is a group V/VI, intrinsic p-type semiconductor and exhibits photo-induced phase-change properties. The other principal arsenic sulfide is As₄S₄, a red-orange solid known as the mineral realgar.