Sulfuric acid, also known as sulphuric acid, is a mineral acid composed of the elements sulfur, oxygen, and hydrogen, with the molecular formula H2SO4. It is a dense, colorless, odorless, and viscous liquid that is miscible with water. Anhydrous H2SO4 is a very polar liquid, having a dielectric constant of around 100, and it has a high electrical conductivity, a consequence of autoprotolysis, i.e. self-protonation. Sulfuric acid is a very strong acid; in aqueous solutions, it ionizes completely to form hydronium ions (H3O+) and hydrogen sulfate ions (HSO4−) . Hydrogen sulfate ions further ionize in very dilute solutions to give sulfate ions (SO42-) .

Sulfuric acid is one of the most commercially important of all chemicals, with large-scale uses in a wide range of industries. It is used in making fertilizers, the production of steel and iron, chemical manufacturing industries, petroleum refining, and to produce phosphoric acid. It is also used as a cleaning agent in industries to remove rust from steel and iron.

Sulfuric acid is a corrosive substance that can be destructive to the skin, eyes, teeth, and lungs. Severe exposure can result in death, and workers may be harmed from exposure to sulfuric acid.