We present an updated synopsis of Oleandra for the Neotropics. For this region, we recognize 20 species plus two putative hybrids. Among these, two species and two hybrids are described as new: Oleandra aequatorialis (endemic to Ecuador), O. arbuscula (from Colombia and northern Brazil), O. × afrobrasiliana (endemic to southeastern Brazil), and O. × nigrovenia (endemic to Venezuela). Within the Neotropics, the main center of diversity of the genus is the sub-Andean regions of Colombia, which harbor eight species. The Brazilian Atlantic Forest is also important, as it harbors four micro-endemic and one endemic species, as well as one hybrid. The other two important regions for the genus diversity are the sub-Andean regions of Venezuela and the mountains of Costa Rica. Oleandra articulata is widespread in the Neotropics, occurring from Mexico and the Antilles to Bolivia, but not occurring in eastern South America (i.e., in the Brazilian Atlantic Forest). On the other hand, we propose to narrow the circumscription of O. pilosa as a species restricted to the Amazon and the Guianan Shield. Segregates from O. pilosa sensu lato are: Oleandra arbuscula, O. hovenkampii, and O. steyermarkii. Three species (O. hovenkampii, O. lehmannii, and O. zapatana) present intriguing disjunct distributions. We present a key to the species and type data, full and new synonymies, descriptions, and illustrations for all taxa. We also choose a lectotype for O. trujillensis and a neotype for O. micans.
