The subfamily Gymnonereidinae (sensu Fitzhugh, 1987) is represented in Australian waters by 14 species in seven genera, of which five are new species and these are described: Ceratocephale aureola n.sp., C. setosa n.sp., Gymnonereis minyami n.sp., G. yurieli n.sp. and Nicon rotunda n.sp. Six species are new records for Australian waters. This subfamily of nereidids is characterised by the lack of chitinous pharyngeal papillae, although soft papillae may be present. A key to the subfamilies of the family Nereididae is given together with a key to the genera and Australian species of the subfamily Gymnonereidinae. This paper represents the first of a series which will describe the Australian nereidid fauna.