Three species of Micronephthys inhabit Northern European and Arctic waters: Micronephthys minuta (Theel, 1879), M. neotena (Noyes, 1980), and M. hartmannschroederae Jirkov et Dnestrovskaya, 2001. All species are re-described, original illustrations and distribution maps accompany all descriptions. Micronephthys minuta and M. neotena are a mainly Arctic and boreal species, respectively, very abundant in brackish waters. Micronephthys hartmannschroederae should be very abundant sporadically in boreal European waters. The existing literature on biology and distribution of these species is reviewed. The taxonomic characters used to separate genera within Nephtyidae are analysed, proving that the family needs to be fully reviewed.
