A comprehensive taxonomic revision of the genus Adelia (Euphorbiaceae s.s.) is presented. Although fourteen species have previously been recorded in the genus, we recognize only nine species based on observations of herbarium material and living plants. The utility of specific taxonomic characters is also evaluated, with particular emphasis on leaf characters as well as characters from staminate and pistillate flowers. Detailed taxonomic descriptions are given for every species including phenological data and iconography. Adelia tenuifolia is excluded from the genus, because it was concluded that it belongs in Bernardia as initially described.