ó-Hydroxybutyraldehyde is the organic compound with the formula HOCH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CHO. It is a colorless liquid. The compound occurs in nature and is produced commercially.
It is a chemical intermediate in the biosynthesis of the neurotransmitter ó-hydroxybutyric acid (GHB) from 1,4-butanediol (1,4-BD). Like 1,4-BD, it also behaves as a prodrug to GHB when taken exogenously. However, as with all aliphatic aldehydes, ó-hydroxybutaldehyde is caustic and is strong-smelling and foul-tasting; thus, actual ingestion of this compound is likely to be unpleasant and result in severe nausea and vomiting.