Cladonia rangiferina, also known as reindeer cup lichen, reindeer lichen (cf. Sw. renlav) or grey reindeer lichen, is a light-colored fruticose, cup lichen species in the family Cladoniaceae. It grows in both hot and cold climates in well-drained, open environments. Found primarily in areas of alpine tundra, it is extremely cold-hardy. Reindeer lichen, like many lichens, is slow growing (3–11 mm per year) and may take decades to return once overgrazed, burned, trampled, or otherwise damaged.