Pannaria formosana is a species of corticolous (bark-dwelling), squamulose (scaley) to foliose (leafy) lichen in the family Pannariaceae.

The type specimen was collected in February, 1965 by Syo Kurokawa from Chinsueiin Pass, (Taitung Prefecture, Taiwan).

The lichen forms brown, circular patches up to about 5 cm (2 in) in diameter with lobes up to 2 mm wide.

The PD+ (orange) chemical spot test reaction indicates the presence of parietin, a lichen product.

Pannaria formosana is found in the lowland forests of southern Taiwan and Honshu, Japan, although the author suggests a potentially wider distribution in the islands of Southeast Asia.