To prepare for a revision of Guapira Aubl. in Brazil, this work proposes nomenclatural changes, typifications, and synonyms. We report twelve more species for the Brazilian flora, including the description of a new species, Guapira candanga, and resurrection of eleven names previously in synonymy. We rearrange the synonymy of some names, combine seven Pisonia species under Guapira, as G. apolinarii, G. cuneifolia, G. darwinii, G. florida, G. heterophylla, G. laurifolia, and G. platystemon, and designate lectotypes for four names.