Ricinocarpos megalocarpus is a species of flowering plant in the family Euphorbiaceae and is endemic to the south coast of Western Australia.

Ricinocarpos megalocarpus is a compact, rounded, usually monoecious, rarely dioecious shrub that typically grows to height of up to 2.5 m (8 ft 2 in), its young branchlets glabrous.

[2][3] Ricinocarpos megalocarpus was first formally described in 2007 by David Halford and Rodney Henderson in the journal Austrobaileya from specimens collected by Paul Wilson in the Duke of Orleans Bay in Cape Le Grand National Park in 1968.

[2][4] The specific epithet (megalocarpus) means "large-fruited", referring to the fruits compared to those of the similar R.

[2][5] This species grows in heath on coastal sand dunes between Cape Le Grand and Cape Arid National Park, in the Esperance Plains, Mallee and Swan Coastal Plain bioregions of south-western Western Australia.