三硫化二锑，别名硫化锑、硫化亚锑，分子式Sb₂S₃。分子量339.68。

黄红色无定形粉末。相对密度4.12。熔点550°C。不溶于水、乙酸，溶于浓盐酸、硫氢化铵、硫化钾溶液和醇。

三硫化二锑化学性质在室温下稳定，但在空气中加热可以得到相应的氧化物，也可被H₂或Fe还原成单质锑。

三硫化二锑溶解在浓盐酸中发生如下反应：

Sb₂S₃+6H+8Cl→2SbCl₄+3H₂S↑

三硫化二锑可以溶解在浓盐酸中，而三硫化二砷不可以（因为三硫化二砷的酸性比三硫化二锑强），因此用此方法可以从三硫化二砷中分离和鉴别锑。

Antimony trisulfide Sb₂S₃ is found in nature as the crystalline mineral stibnite and the amorphous red mineral metastibnite. It is manufactured for use in safety matches, military ammunition, explosives and fireworks. It also is used in the production of ruby-colored glass and in plastics as a flame retardant. Historically the stibnite form was used as a grey pigment in paintings produced in the 16th century. It is a semiconductor with a direct band gap of 1.8-2.5 eV. With suitable doping p and n type materials can be produced.