thumb|right|alt=Pale grey to tan leafy lichen growing on rock, with broad leathery lobes and black, curled margins exposing the darker underside |Smooth rock tripe ([[Umbilicaria mammulata) growing on rock]]
Rock tripe is a common name for edible rock-dwelling lichens, especially species of Umbilicaria. The term is vernacular rather than taxonomic, and its scope has varied by region and source. In North America, rock tripe was known primarily as a famine food, eaten by Cree, Inuit, and other Indigenous peoples and later by European explorers and voyageurs during periods of extreme scarcity. In East Asia, by contrast, Umbilicaria esculenta has been valued as a delicacy in Japanese, Korean, and Chinese cuisine since at least the 17th century. The English name derives from the Canadian French expression .
Rock tripe requires extensive processing, typically soaking and repeated boiling, to reduce bitter secondary metabolites such as gyrophoric acid that otherwise cause severe gastrointestinal distress. The principal carbohydrate in Umbilicaria is pustulan, which humans digest poorly, so the lichens provide less usable nourishment than their dry mass might suggest. They also contain bitter secondary metabolites, especially gyrophoric acid, which may help explain the nausea and bowel complaints described in historical accounts. Rock tripe is best known in Western historical writing for its role during John Franklin's disastrous overland Arctic expedition of 1819–1822, when it was one of the few available foods as the party retreated across the Barren Grounds. Because Umbilicaria lichens grow very slowly, heavy harvesting can deplete local populations for long periods.
Terminology
Historical lexicography defines rock tripe as an edible lichen of the genus Umbilicaria, or less often of the former genus Gyrophora.
</references>