A new species of Meriania (Melastomatacea; Merianieae) endemic to the Brazilian Atlantic Forest is described and illustrated. Meriania paratyensis is known only from a single locality in the Joatinga Ecological Reserve, municipality of Paraty, in Rio de Janeiro State. The diagnostic characteristics and comparisons with similar species, geographic distribution, and a conservation assessment using IUCN guidelines are presented for the new species, as well as a key to identify all Meriania species known from the Atlantic Forest.