Marianthus mollis, commonly known as hairy-fruited billardiera,[2] is a species of flowering plant in the family Pittosporaceae and is endemic to a small region in the southwest of Western Australia.

It is an erect, spreading, silky-hairy shrub with sessile, egg-shaped leaves and purplish-blue flowers arranged singly in leaf axils.

[2][3][4] This species was first formally described in 1983 by Eleanor Marion Bennett, who gave it the name Billardiera mollis in the journal Nuytsia, from specimens she collected on the "north-east slope of the southern ridge of the Ravensthorpe Range" in 1979.

[7] Marianthus mollis is only known from the area near where the type collection was made, where it grows in open mallee and tall shrubland in the Esperance Plains bioregion of south-western Western Australia.

[3][2] Marianthus mollis is listed as "Priority Four" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions,[2] meaning that it is rare or near threatened.