Ocellularia flavescens is a species of corticolous (bark-dwelling) lichen in the family Graphidaceae.

Found in northern Thailand, it was formally described as a new species in 2002 by lichenologists Natsurang Homchantara and Brian J. Coppins.

The type specimen was collected from Doi Suthep National Park (Chiang Mai Province); here it was found in an oak/chestnut forest at an elevation of 1,600 m (5,200 ft).

The presence of this chemical causes the lichen thallus to fluoresce a golden-yellow colour when lit with a long-wavelength (365 nm) UV light.

This feature is referenced in its specific epithet flavescens (Latin for "becoming yellow or golden").