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 a characteristic odor that has been described as "ammoniacal, fishy, shellfish-like".In addition to pyrrolidine itself, many substituted pyrrolidines are known.