Updated checklist of polychaete species (Annelida) recorded from Malaysia, with remarks on the research history.

Background: An updated comprehensive checklist of polychaete species, which have been recorded from Malaysian waters, is provided, with their geographic distributions and the research history for them. A total of 57 species belonging to 30 families have been reported since the early 1870s, with Nereididae as the most dominant family with ten species; however, more than half of the total are questionable species in the country. Despite the increased efforts of polychaete studies in the past decade, the taxonomic endeavour of discovering and describing species in the country could be higher. Malaysian polychaetes were mostly recorded from Peninsular Malaysia, whereas very few were from Borneo Island. Most previously recorded species were associated with intertidal and estuarine habitats and a few were found in the subtidal and freshwater environments. We stress the need for urgent research on this biologically, ecologically and culturally relevant taxonomic group as the species accumulation curve grows exponentially in this megadiverse country. New information: The current checklist has been updated since the previous one in 2013. Many species previously listed were judged as doubtful and not taxonomically reliable.