A new obligately cavernicolous planthopper species belonging to the Delphacidae was discovered in a cave in Bahia State, Brazil. As no epigean relatives could be identified so far, the species is isolated among the Asiracinae, and accordingly, a new genus Spelaeodelphax gen. nov. is erected to accommodate it. Worldwide, this discovery represents only the fourth record of subterranean Delphacidae and the second confirmed case of a cave-adapted delphacid, and the first such record in the Americas. The Spelaeodelphax nexus sp. nov. is the seventh troglobiont Fulgoromorpha recorded in Brazil. The discovery of this spectacularly troglomorphic species is yet another example of the unique diversity and ecological complexity of biological communities in Brazilian cave environments, and underlines the imperative need for the conservation and in-depth study of subterranean ecosystems.