Hesionid interrelationships are assessed in a parsimony analysis of 97 (86 informative) absent/present coded morphological characters of 37 terminal taxa within the group. Character information is based on examination of available types, newly collected topotypes and additional non-types, with introduction of many not previously recorded characters. Polarity is assessed differently in two separate analyses, one by outgroup comparison with nereids and chrysopetalids, yielding two equally parsimonious trees, and one by observations from juvenile hesionids, yielding 10 equally parsimonious trees. The outgroup rooted trees are selected for a reclassification, and three main groups are recognised: Hesiolyrinae, new subfamily, Hesioninae Grube, 1850, and Ophiodrominae, new subfamily. Hesiolyrinae is monotypic for Hesiolyra, Hesioninae includes Hesionini Grube, 1850 and Psamathini, new tribe, and Ophiodrominae includes Gyptini and Ophiodromini, both new tribes. Sirsoe, new genus and member of Psamathini, is established for Orseis grasslei Blake, 1985 and the yet undescribed Sirsoe A. High degrees of homoplasy are demonstrated for a number of characters traditionally used in hesionid taxonomy, e.g., distribution of anterior, enlarged cirri, and first segment provided with neurochaetae and neuropodial lobes. Diagnoses and descriptions are provided for all supraspecific hesionid taxa and a checklist of hesionids is included. For improved precision in polychaete descriptions it is suggested that the term ‘tentacular cirri’ should be replaced by ‘anteriorly situated cirri’ with specified position and morphology. The following new generic synonyms are introduced: Lamproderma Grube, 1877, objective junior synonym of Leocrates Kinberg, 1866; Neopodarke Hartman, 1965 junior synonym of Nereimyra Blainville, 1828; Orseis Ehlers, 1864, junior synonym of Ophiodromus Sars, 1862; Paragyptis Pocklington, 1984 junior synonym of Gyptis Marion & Bobretzky in Marion, 1874; and Podarke Ehlers, 1864, objective junior synonym of Ophiodromus. Additionally a number of new species group synonyms and new combinations are proposed. Parallel to the Linnaean, type-based definitions of taxon names, a hesionid classification is introduced with phylogenetic taxon name definitions.