Merianthera is a genus endemic to rocky outcrops in eastern Brazil, with seven species, four of which are new and described here (M. bullata, M. eburnea, M. parvifolia, M. verrucosa). The genus can be recognized by its caducous leaves, inferior ovaries and dry, rupturing fruits, as well as by the stamens with complex dorsal appendages. Merianthera is monophyletic, and sister to a clade consisting ofDolichoura, Behuria and Huberia (all from tribe Merianieae); together these four genera are sister to Cambessedesia, but not closely related to other genera in tribe Merianieae, such as Meriania and Graffenrieda. Within the genus, there are two distinct clades, the first with two species with thite to pink petals and leaves abaxially covered with a dense indument, both growing on sandstone and endemic to Minas Gerais (M. eburnea, M. sipolisii). The other clade comprises the remaining five species, all with glabrous or glabrescent leaves and purple petals, growing on granitic/gneissic outcrops and endemic to Espirito Santo (M. bullata, M. burlemarxii, M. parvifolia) or occurring in this state and also Minas Gerais (M. verrucosa) or in both plus Bahia (M. pulchra).