Diazepam is a drug. It is a benzodiazepine which has a relatively long half-life. It is mostly used to treat anxiety, certain forms of epilepsy, and sleeping problems. Like with other benzodiazepines, there is a risk of addiction. For this reason the drug is used to treat acute cases. It should not be taken for longer than a few weeks. According to the World Health Organization diazepam is an essential drug.
Diazepam is marketed under a number of names; its original trade name was Valium. It is one of the drugs prescribed most often. It is used recreationally to cause a calming effect.