Ricinocarpos marginatus is a species of flowering plant in the family Euphorbiaceae and is endemic to the north-west of Western Australia.

Female flowers are on a stout pedicel 6–15 mm (0.24–0.59 in) long and have narrowly oblong, white petals covered on both sides with soft, star-shaped hairs.

[2][3] Ricinocarpos marginatus was first formally described in 1873 by George Bentham in Flora Australiensis from specimens collected by Allan Cunningham on the north-west coast of Western Australia.

[6] This species grows in woodland amongst sandstone rocks in the Northern Kimberley bioregion of north-western Western Australia.

[2][3] Ricinocarpos marginatus is listed as is classified as "Priority Two" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions, meaning that it is known from only few locations some of which are not thought to be under immediate threat.