Azetidine is a saturated heterocyclic organic compound containing three carbon atoms and one nitrogen atom. It is a liquid at room temperature with a strong odor of ammonia and is strongly basic compared to most secondary amines.
Azetidine and its derivatives are relatively rare structural motifs in natural products. Notably, they are a key component of mugineic acids and penaresidins. Perhaps the most abundant azetidine containing natural product is azetidine-2-carboxylic acid, a non-proteinogenic homolog of proline.