SummaryNumidian King Juba II (48 BCE–23/24 CE) ruled the north‐western African Roman client kingdom of Mauretania between the year 25 BCE until his death. During his patronage natural history expeditions were undertaken in Africa. The Canary Islands were among the areas whose exploration he sponsored, and this represented the earliest survey of the natural history of this archipelago. Juba II is considered to be one of the most important promoters of the study of geography, fauna, and flora in ancient times. His writings are lost, but the Roman army officer and naturalist Pliny the Elder (Caius Plinius Secundus, 23/24–79 CE) had access to them, and in his multivolume work Naturalis Historia provided extensive accounts of Juba's natural history descriptions. Relevant for our research, they included the earliest known report for the genus Euphorbia (as “Euphorbea” in Pliny's work). Eponyms for four generic names, three specific epithets, and one varietal name celebrate the legacy of Juba II. Here we provide an overview of the biogeography and phylogenetics of these taxa, with an emphasis on the Canary Island endemic E. regis‐jubae Webb & Berthel. We also discuss Pliny's description of Euphorbia and highlight the importance of eponyms to provide insights into the botanical history of Macaronesia.