The new species of millipede Cylindroiulus villumi is described from a cave in the Estremenho karst massif in central Portugal. It is the first cave-adapted species of its genus with a strict subterranean life-style in continental Europe, and is the fifth blind species of the genus. The new species is illustrated with photographs and diagrammatic drawings. It is tentatively placed in the purely Iberian Cylindroiulus perforatus-group. The differences between the new species and its relatives are discussed, as well as its adaptations to a subterranean life-style.