An amine is an organic compound formed by replacing one or more of the hydrogen atoms in the ammonia molecule (NH₃) by alkyl groups or aryl groups. Primary amines have general formula RNH₂; secondary R₂NH; tertiary R₃N. Heterocyclic nitrogen bases (including the alkaloids and pyridine) are tertiary amines.

Amines may be formed by reduction of amides, nitriles, or nitro compounds, or by reaction of ammonia with organic halides, alcohols, or sulfonic acids. They are produced in nature by the putrefaction of organic matter.

Simple amines are pungent liquids which are strong bases and ligands; many occur naturally in decaying organic matter. They give amides with acid derivatives. All amines react with nitrous acid (dilute hydrochloric acid and sodium nitrate) but the product varies according to the number and type of hydrocarbon units attached to the nitrogen atom in the amine group. If the amino group is attached directly to a hydrocarbon ring and the reaction is carried out at 5°C or below, a diazonium salt is formed. Diazonium salts are the starting points in the manufacture of azo dyes. Amines are also used in the manufacture of many drugs and synthetic fibers.