Subantarctia trina is a species of Orsolobidae. The species is endemic to New Zealand.
This species was described in 1985 by Ray Forster and Norman Platnick from male and female specimens collected near Dunedin. The holotype is stored in Otago Museum.
The male is recorded at 4.08mm in length whereas the female is 5.20mm.
This species is restricted to the coastal area of Otago, New Zealand.
Under the New Zealand Threat Classification System, this species is listed as "Naturally Uncommon" with the qualifiers "Range Restricted".