Megalopta (Smith 1853) is a nocturnal and/or crepuscular bee genus, with Neotropical distribution. The present work presents a taxonomic revision of Megalopta with emphasis on the Brazilian species through diagnosis and description of species and an identification key for most species that occur in South and Central America, with figures and distribution maps. Moreover eight new species are described: Megalopta guarani sp. n, M. mura sp. n, M. piraha sp. n, M. munduruku sp. n, M. yanomami sp. n, M. xavante sp. n, M. mapinguari sp. n. and Megalopta karitiana sp. n. Sex association for the male of M. chaperi (Vachal, 1904) is presented. Also we present taxonomical notes of valid species, with designation of lectotypes, new synonymies and checklist of valid species. Now, 32 valid species are recognized for the genus, with 19 in the Brazilian fauna. The present work enables correct identification of the species, which should facilitate further studies with Megalopta.