Parmelia is a genus of medium to large foliose (leafy) lichens. It has a global distribution, extending from the Arctic to the Antarctic continent but concentrated in temperate regions. There are about 40 species in Parmelia. In recent decades, the once large genus Parmelia has been divided into a number of smaller genera according to thallus morphology and phylogenetic relatedness.

It is a foliaceous lichen, resembling a leaf in shape. The ends of the leaf-like lobes are often squarish-tipped. The upper surface is pale bluish-gray to light brown in direct sunlight, with a network web-like ridges and depressions. The lower surface is black and has rhizines anchoring it to the substrate. In general, Parmelia have a dark lower side with rhizines ('rootlets') that attach the lichen to its substrate. The upper side may be several colours - grey, yellow, brown - and may have reproductive organs on it. These may be apothecia (ascospore-producing bodies), isidia or soralia (both vegetative structures). In between these two layers is the medulla, which contains the algal component of the lichen.

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