Byssoloma brunneodiscum is a species of foliicolous (leaf-dwelling) lichen in the family Pilocarpaceae.

The type specimen was collected by Wang in the Mingfeng Valley of Jianfeng Ridge (Ledong County, Hainan) at an altitude of 960 m (3,150 ft).

It is only known to occur at high-altitude rainforests on Hainan Island, where it grows sparsely on leaf surfaces in the damp understorey.

The specific epithet brunneodiscum refers to the brown discs that are characteristic of the apothecia of this species.

Byssoloma annuum is similar in appearance and chemistry, but is distinguished from B. brunneodiscum by its orange-yellow apothecia and colourless hypothecium.