Marianthus sylvaticus is a species of flowering plant in the family Pittosporaceae and is endemic to a small area in the southwest of Western Australia.

It is a slender climber with clustered, toothed, linear leaves and blue and white flowers with purple veins.

Marianthus sylvaticus is a slender climber that has sparsely hairy, reddish brown stems with prominent lenticels.

[2][3][4] Marianthus sylvaticus was first formally described in 2004 by Lindy W. Cayzer and Michael Crisp in Australian Systematic Botany from specimens collected in the Walpole-Nornalup National Park.

[2][4] Marianthus sylvaticus is listed "not threatened" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions.