Hieronyma crassistipula is a species of plant in the family Phyllanthaceae, which was recently separated from the Euphorbiaceae. It is a tree endemic to Cuba's Isla de la Juventud.
It is native to gallery forests growing on quartzite sand from 5 to 15 meters elevation. It is an extremely rare plant, with fewer than 50 mature individuals known from three locations. It is threatened by habitat loss from deforestation and non-native invasive plants. The IUCN Red List assesses the species as Critically Endangered.