Liberty cap (Psilocybe semilanceata) is a hallucinogenic mushroom , a so called magic mushroom, that grows on grassy meadows and similar; particularly in fields and other habitats well fertilised by sheep and other cattle dung (although unlike Psilocybe cubensis it does not grow directly on dung). It grows in various places throughout the world, but is known primarily as a native of Europe, growing throughout continental Europe, the UK and Ireland.

Liberty cap is also the name of a type of hat, also known as a Phrygian cap. The mushroom was named for its resemblance to this headgear.