A taxonomic synopsis of the family Nephtyidae in Chile is made. A review of the data concerning the species known from Chile is given and a new specific entity, Nephtys (Nephtys) monilibranchiata n.sp., closely related to N. (N.) impressa Baird, is described. In accordance with the facts known up to now, two subgenera - Nephtys and Aglaophamus - represent the family in Chilean seas, including the Antarctic. These sub-genera comprise a total of 19 species and one sub-species. The following is the list of the Chilean Nephtys species: N. (A.) erectanoides Hartmann?Schröder N. (A.) foliosus Hartman N. (A.) heteroserrata Hartmann?Schröder N. (A.) lutrea Baird N. (A.) macroura Schmarda N. (A.) ornatus Hartman N. (A.) ornatus bransfieldia Hartman N. (A.) peruana Hartman N. (A.) polyphara Schmarda N. (A.) posterobranchus Hartman N. (A.) virginis Kinberg N. (A.) ferruginea Hartman N. (N.) glossophylla Schmarda N. (N.) imbricata Grube N. (N.) impressa Baird N. (N.) magellanica Augener N. (N.) monilibranchiata n.sp. N. (N.) oculata Hartmann-Schröder N. (N.) paradoxa Malm N. (N.) serratifolia Ehlers Material from 6 species was revised: N. (A.) macroura, N. (A.) peruana, N. (A.) polyphara, N. (N.) ferruginea, N. (N.) impressa, and N. (N.) serratifolia. For the comparative analysis the holotype of N. impressa Baird, deposited in the British Museum of Natural History, was investigated.