Lorazepam, sold under the brand name Ativan among others, is a benzodiazepine medication. It is used to treat anxiety disorders, trouble sleeping, severe agitation, active seizures including status epilepticus, alcohol withdrawal, and chemotherapy-induced nausea and vomiting. It is also used during surgery to interfere with memory formation and to sedate those who are being mechanically ventilated. It is also used, along with other treatments, for acute coronary syndrome due to cocaine use. It can be given by mouth or as an injection into a muscle or vein. When given by injection onset of effects is between one and thirty minutes and effects last for up to a day.

Common side effects include weakness, sleepiness, low blood pressure, and a decreased effort to breathe. When given intravenously, the person should be closely monitored. Among those who are depressed, there may be an increased risk of suicide. With long-term use, larger doses may be required for the same effect. Physical dependence and psychological dependence may also occur. If stopped suddenly after long-term use, benzodiazepine withdrawal syndrome may occur. Older people more often develop adverse effects. In this age group, lorazepam is associated with falls and hip fractures. Due to these concerns, lorazepam use is generally only recommended for up to two to four weeks.

Lorazepam was initially patented in 1963 and went on sale in the United States in 1977. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2020, it was the 65th most commonly prescribed medication in the United States, with more than 10 million prescriptions.