A new species of Eunicidae, Marphysa victori sp. n., has been identified from Arcachon Bay, Bay of Biscay, NE Atlantic. This new species, belonging to the sanguinea complex, is characterised by branchiae with long filaments from chaetigers 26–34, the presence of four types of pectinate chaetae with first ones present from chaetiger 2, a large number of both pectinate chaetae and compound spinigers, and the pygidium with only one pair of pygidial cirri. An identification key for European species of the genus Marphysa is provided.