A vast polychaete fauna is hidden behind complexes of cryptic and pseudo-cryptic species, which has greatly hindered our understanding of species diversity in several regions worldwide. Among the eunicids,Marphysa sanguineaMontagu, 1813 is a typical example, recorded in three oceans and with various species considered its junior synonyms. In South Africa, specimens previously misidentified asM. sanguineaare now known asMarphysa elityeniLewis & Karageorgopoulos, 2008. Of the sixMarphysaQuatrefages, 1865a species recorded from the same region, three have their distributions restricted to South Africa while the others are considered to have worldwide distributions. Here, we evaluated the taxonomic status of the indigenousM. elityeniand investigated the presence of the widespread speciesMarphysa macintoshiCrossland, 1903 andMarphysa depressaSchmarda, 1861 in South Africa using morphological and molecular data. Our results reveal thatM. elityeniis a junior synonym ofMarphysa haemasoma, a species previously described from South Africa which is herein reinstated as a valid species. BothM. macintoshiandM. depressaare not present in South Africa and their status as being distributed worldwide deserves further investigation.Marphysa durbanensisDay, 1934 and the new species described here,M. sherlockaen. sp., had been misidentified asM. macintoshiandM. depressarespectively. Thus, the number ofMarphysaspecies with distributions restricted to South Africa increased from three to five. This study reiterates the importance of implementing an integrated taxonomic framework to unravel local biodiversity.