The identity of the enigmatic Thibaudia ardisiifolia (Ericaceae: Vaccinieae) is clarified. It is shown that a mixed gathering consisting of leaves of Clusia ducuoides (Clusiaceae) and flowers of a Thibaudia species served as basis for Kunth when he validated this name. A lectotype in the Willdenow Herbarium is designated, and the correct name, T. floribunda Kunth, is applied to this taxon for the first time. A list of synonyms and a full description of this species, which is native in Venezuela, Colombia, Ecuador, Peru and Bolivia, are also provided together with ecological data. Additionally, Cuatrecasas's incorrect interpretation of the unpublished name T. arbutifolia and the confusion it caused are discussed, and the correct name Macleania rupestris (Ericaceae: Vaccinieae) is applied. Citation: Luteyn J. L. & Lack H. W. 2026: Thibaudia ardisiifolia (Ericaceae: Vaccinieae): an enigma solved and a new synonymy provided for T. floribunda. – Willdenowia 56: 419–426 Version of record first published online on 4 September 2026.
