Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula (CH₂)₄NH. It is a cyclic secondary amine, also classified as a saturated heterocycle. It is a colourless liquid that is miscible with water and most organic solvents. It has an ammonia-like, but characteristic odor. In addition to pyrrolidine itself, many substituted pyrrolidines are known.

Pyrrolidine is produced by treatment of 1,4-butanediol with ammonia over an oxide catalyst.

Many modifications of pyrrolidine are found in natural and synthetic chemistry. The pyrrolidine ring structure is present in numerous natural alkaloids such as nicotine and hygrine. It is found in many drugs such as procyclidine and bepridil. It also forms the basis for the racetam compounds (e.g. piracetam, aniracetam). The amino acids proline and hydroxyproline are, in a structural sense, derivatives of pyrrolidine.

Pyrrolidine is a base. Its basicity is typical of other dialkyl amines. Relative to many secondary amines, pyrrolidine is distinctive because of its compactness, a consequence of its cyclic structure.

Pyrrolidine is used as a building block in the synthesis of more complex organic compoundsi. It is used to activate ketones and aldehydes toward nucleophilic addition by formation of enamines:

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