Ectinosomatid material was examined from extensive collections around the British Isles and from several additional world localities and museum collections, permitting a revision of the genus Halectinosoma. This paper redescribes H. herdmani and describes five new species: H. bodotriaensis sp. nov., H. pilosum sp. nov., H. britannicum sp. nov., H. itoi sp. nov. and H. huysi sp. nov. These species, together with H. tenerum (Sars) and H. kunzi Lang, are referred to the 'herdmani species group', on the basis of close similarity. H. herdelongata (Marcus) is synonymized with H. herdmani. H. elongatum (Sars), previously regarded as incertae sedis, is also redescribed. Despite a superficial resemblance to the herdmani group of species, H. elongatum was found to be morphologically quite distinct. H. intermedium (Nicholls) was found to be a synonym of H. elongatum. The species H. finmarchicum (T. Scott) is discarded; the original description was found to be based largely on material of H. elongatum but mistakenly included the female fifth leg from H. angulifrons (Sars). A key for the identification of females of the herdmani group of species is provided.