A new species, Euphorbia adenoplicata, is here described and illustrated. The species was found in the vicinity of Serra Geral do Tocantins, close to the border of the states of Tocantins and Bahia, within the Cerrado biome, where it grows in cerrado rupestre (rocky savannah vegetation). Euphorbia adenoplicata is placed in Euphorbia sect. Crossadenia based on morphological characters. The species is unique within the section due to its cyathial glands with the margins folded in the middle portion, splitting each gland into two cavities. We compare the morphology and ecology of E. adenoplicata with E. sarcodes and other species of E. sect. Crossadenia subsect. Ephedropeplus. Finally, we recommend that E. adenoplicata be considered critically endangered due to its extreme rarity.