Marianthus microphyllus is a species of flowering plant in the family Pittosporaceae and is endemic to the south of Western Australia.

It is a small, erect, spreading shrub with clustered, funnel-shaped, stem-clasping leaves and deep blue to almost purple flowers that darken as they age, arranged singly in leaf axils.

Marianthus microphyllus is an erect, spreading shrub with sharp, hairy side shoots.

Flowering mainly occurs from September to November and the fruit is a blue capsule 7–8 mm (0.28–0.31 in) long that turns brown as it ages.

[3][2] This marianthus is listed as "not threatened" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions.