The genus Ephemera Linnaeus, the type genus of the family Ephemeridae and the order Ephemeroptera, began to be studied as early as in the nineteenth century, but the East Asian species of Ephemera remained poorly understood. In this paper, 16 Ephemera species from tropical Southeast Asia are reviewed and descriptions of new or poorly known species and life stages, synonyms, reference sources, type information, taxonomic remarks, a male adult key to the species, and a tabulated checklist of the species are provided. Ephemera mccaffertyi sp. n. from Malaysia is described. Ephemera hainanensis Zhang, Gui & You, E. rufomaculata Zhou & Zheng, and E. spilosa Navás are redescribed. The larval stage of E. hainanensis and E. spilosa are described. Ephemera innotata Navás, E. javana Navás, E. longiventris Navás, and E. quadrigutata Lestage are assigned as nomina dubia. As a result of this study, four species from Vietnam, four species from Myanmar, two species from Thailand, one new species from Malaysia, and three species from Taiwan have been identified as members of the genus Ephemera.