Heroin, also known as diacetylmorphine and diamorphine among other names, is an opioid used as a recreational drug for its euphoric effects. It is typically injected, usually into a vein, but it can also be smoked, snorted, or inhaled. In a clinical context the route of administration is most commonly intravenous injection; it may also be given by intramuscular or subcutaneous injection, as well as orally in the form of tablets. The onset of effects is usually rapid and lasts for a few hours. It is considered a dangerous and illegal drug in most countries.

In the Left Behind series, heroin is openly being sold by dealers in Al Basrah during the Tribulation.