Reestablishment and a new name for <i>Actinostemon grandifolius</i> (Müll.Arg.) Pax

The genus Actinostemon has undergone several changes in its circumscription due to persistent difficulties in its taxonomic placement. The taxonomic history of the genus is controversial and marked by nomenclatural issues, particularly involving its type species, Actinostemon grandifolius Klotzsch, including incorrect synonymizations and the publication of a nomen nudum . Based on the analysis of herbarium specimens, protologues, and original material, we reestablish Actinostemon grandifolius (Müll.Arg.) Pax and propose Actinostemon macrophyllus Oliv.‐Souza &amp; Külkamp as its new name, which had been previously recognized as a posterior homonym and synonymized under Actinostemon klotzschii (Didr.) Pax. We provide a diagnosis, morphological descriptions, a distribution map, illustrations, notes on phenology, preliminary conservation status, taxonomic comments, and a detailed discussion of the taxonomic implications, assigning a lectotype to the reestablished species.