Pterostylis williamsonii, commonly known as the brown-lip leafy greenhood, is a plant in the orchid family Orchidaceae and is endemic to Tasmania.

Pterostylis williamsonii, is a terrestrial, perennial, deciduous, herb with an underground tuber.

[3][4][5] Pterostylis williamsonii was first formally described in 1998 by David Jones and the description was published in Australian Orchid Research from a specimen collected by Ron and Kath Williamson at Coles Bay.

[1][4] The specific epithet (williamsonii) honours Ronald Herbert Williamson (1931-2003), who collected the type specimen.

[5] The brown-lip leafy greenhood is widespread in Tasmania where it grows in forest near low shrubs and bracken.