Potassium sulfate (K₂SO₄)is a colorless compound having rhombic or hexagonal crystals. It readily forms double salts with the sulfate of trivalent metals, which are known as Alums. It also forms double salts with calcium, magnesium and sodium sulfates. It is widely employed as a fertilizer. K₂SO₄ can be extracted from various complex salts in nature, such as Kainite, langbeinite and carpathein mineral ores. It can be synthesized by reacting KCl and sulfuric acid, via Mannheim process.

Potassium sulfate is a water-soluble inorganic salt that is commonly used in fertilizers. It can be prepared by reacting phosphogypsum and potassium chloride. K₂SO₄ can form needle-like mullite particles on heating with aluminum sulfate and silicon dioxide. Its application to the soil has shown to minimize bronzing of rice plants.

Potassium sulfate may be used as a sulfonating agent in the preparation of 4′-dibenzo-18-crown-6-sulfonic acid via sulfonation of dibenzo-18-crown-6.

Potassium sulfate may be used in the preparation of needlelike mullite particles. It may be used as a buffer for minimizing the adsorption of proteins on fused-silica capillaries in capillary zone electrophoresis.