Ocellularia peremergens is a species of corticolous (bark-dwelling) lichen in the family Graphidaceae. Found in 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 Inthanon National Park (Chiang Mai Province) at an elevation of 2450m (8,040feet). The lichen has a shiny, pale greenish-grey thallus with a finely verruculose (warted) texture and a white medulla. The apothecia occur solitarily, measuring 0.7–1.2 mm in diameter; they are emergent, meaning they project somewhat above the thallus surface. O. peremergens contains fumarprotocetraric acid, a secondary compound.