Osmium tetrasulfide is an inorganic compound, a salt of osmium metal and hydrogen sulfide acid with the chemical formula OsS₄.

Osmium tetrasulfide can be made by passing hydrogen sulfide through acidified solutions of osmium tetroxide:

Osmium tetrasulfide forms dark brown crystals. It does not dissolve in cold water. It is soluble in dilute nitric acid. It forms hydrates.

Osmium tetrasulfide decomposes upon melting.