A new species of Magelonidae, Magelona debeerei sp. nov., is described and illustrated from grab-samples collected at <100 m off the southwest coast of Africa. Magelona debeereisp. nov. has previously been identified from the region as M. papillicornis by Day (1955, 1961, 1967) but differs from M. papillicornis sensu stricto by possessing dorsal medial lobes on chaetigers 4-8 and lateral pouches (Σ configuration) between chaetigers 10 and 11. Three species of Magelona have now been recorded from southern Africa (M. capensis Day, 1961, M. cincta Ehlers, 1908 and M. debeereisp. nov.), and a key to Magelona from this region is provided. Keywords: Polychaeta, Magelonidae, Magelona, southern African waters.