Mangua forsteri is a species of Physoglenidae spider endemic to New Zealand.

[1] This species was described as Linyphia setosa in 1964 by Ray Forster from male and female specimens.

[1] The holotype is stored in Te Papa Museum under registration number AS.000108.

The abdomen is black brown and has a pale pattern dorsally.

[1] Under the New Zealand Threat Classification System, this species is listed as "Not Threatened".