Chloral hydrate, also known as trichloroacetaldehyde monohydrate, 2,2,2-trichloro-1,1-ethanediol, and under the tradenames Aquachloral, Novo-Chlorhydrate, Somnos, Noctec, and Somnote, is a sedative and hypnotic drug as well as a chemical reagent and precursor. Its chemical formula is C₂HCl₃O · H₂O.

It is used for the short-term treatment of insomnia and as a sedative before minor medical or dental treatment. It has been largely displaced by the development of benzodiazepines. It was also formerly used as in veterinary medicine as a general anesthetic. Today, it is commonly used as an ingredient in the veteranary anesthetic Equithesin.

In therapeutic doses for insomnia it is effective within sixty minutes, it is rapidly metabolized into trichloroethanol and trichloroacetic acid. Higher doses can depress respiration and blood pressure. An overdose is marked by confusion, convulsions, nausea and vomiting, severe drowsiness, slow and irregular breathing, cardiac arrhythmia and weakness. It may also cause liver damage. It is moderately addictive. Chronic use can cause dependency and withdrawal symptoms. It can potentiate various anticoagulants and is weakly mutagenic in vitro and in vivo.