Cladonia rangiferina, also known as reindeer cup lichen, reindeer lichen (cf. Sw. renlav) or grey reindeer lichen, is a light-coloured 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.

Other common names include reindeer moss, deer moss, and caribou moss, but these names can be misleading since it is, though somewhat moss-like in appearance, not a moss. As the common names suggest, reindeer lichen is an important food for reindeer (caribou), and has economic importance as a result. Synonyms include Cladina rangiferina and Lichen rangiferinus.

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