Lactuca virosa is a plant in the Lactuca (lettuce) genus, ingested often for its mild analgesic and sedative effects which are similar to those of ibuprofen. It is related to common lettuce (L. sativa), and is often called wild lettuce, bitter lettuce, laitue vireuse, opium lettuce, poisonous lettuce, tall lettuce, great lettuce or rakutu-karyumu-so.
Lactuca virosa is widespread across much of central and southern Europe. It can be found locally in the south east and east of England. In the rest of Great Britain it is very rare, and in Ireland it is absent. It is also found in the Punjab Region of Pakistan India and Australia where it grows in the wild.
In North America, it has been documented as introduced in California, Alabama, Iowa, and Washington, DC, and grows wild in other parts of the continent
Lactuca virosa is biennial, similar to prickly lettuce Lactuca serriola but taller.