This study describes Siphoneugena carolynae (Myrtaceae), a new species from the Brazilian Atlantic Forest, in the state of Rio de Janeiro. The species inhabits inselberg forests and differs from all other species of Siphoneugena by the following exclusive combination of morphological characters: relatively long petioles, leaf blades chartaceous with midvein canaliculate adaxially, inflorescences in racemes with a markedly compressed and indistinguishable main axis, hypanthium markedly constricted above the ovary, calyx calyptrate, ovaries with two locules, each with four ovules, and cotyledons densely covered with foveolate glands. We herein provide taxonomic notes, morphological plates (derived from both fresh and dried material), and a distribution map. Regarding the conservation status, the new species is preliminarily assessed as Data Deficient (DD), but comments on population size and possible threats to the habitat are presented.
