Sulfamic Acid, also known as amidosulfonic acid, amidosulfonic acid, amidosulfuric acid, and aminosulfonic acid, is a molecular compound with the formula H3NSO3. This colorless, water-soluble compound finds many applications.

The most famous application of Sulfamic Acid is in the synthesis of sweet-tasting compounds. Reaction with cyclohexylamine followed by addition of NaOH gives C6H11NHSO3Na, sodium cyclamate. Related compounds are also sweeteners, see acesulfame potassium.

Sulfamic Acid (O-substituted-, N-substituted-, or di-/tri-substituted derivatives of sulfamic acid) have been used in the design of many types of therapeutic agents such as antibiotics, nucleoside/nucleotide human immunodeficiency virus (HIV) reverse transcriptase inhibitors, HIV protease inhibitors (PIs), anti-cancer drugs (steroid sulfatase and carbonic anhydrase inhibitors), anti-epileptic drugs, and weight loss drugs.

Sulfamic Acid is used as an acidic cleaning agent, sometimes pure or as a component of proprietary mixtures, typically for metals and ceramics. It is frequently used for removing rust and limescale, replacing the more volatile and irritating hydrochloric acid. It is often a component of household descaling agents or detergents used for removal of limescale. When compared to most of the common strong mineral acids, Sulfamic acid has desirable water descaling properties, low volatility, low toxicity and is a water soluble solid forming soluble calcium and iron-III salts. Its also finds applications in the industrial cleaning of dairy and brew-house equipment. Although it is considered less corrosive than hydrochloric acid due to its lower pKa, corrosion inhibitors are often added to commercial cleansers of which it is a component. It is possible that the amino group could act as a ligand under certain circumstances, as does the chloride ion for Fe-III, when hydrochloric acid is used in rust removal.