The correct citation for Grevillea manglesii (Proteaceae) is G. manglesii Pépin (1838). A neotype is here selected from among historic collections, now at Paris (P). Should the minimal description provided by Pépin be successfully challenged as inadequate, the name would not change but the revised authority would be Grevillea manglesii (Graham) A.Baumann and N.Baumann (1843). The origins and complex taxonomic and horticultural history of G. manglesii and its synonyms Manglesia glabrata Lindl., Anadenia manglesii Graham, Grevillea manglesii Hort., Manglesia trilobata Hort. ex Ettingsh., and Manglesia cuneata Endl. are outlined and discussed, together with new insights discerned from James Mangles’ unpublished Letter Books. The important role of Captain James Mangles R.N. to the botany and horticulture of Grevillea manglesii is reviewed and historical errors are corrected. Manglesia glabrata Lindl. is lectotypified. G. ornithopoda Meisn. is reinstated at specific rank and G. dissectifolia (McGill.) Olde is published as a new combination. Both are phenetically diagnosable without intergrades and occur in discrete populations that sometimes overlap the distribution of related species.