Stanwellia tuna is a species of mygalomorph spider endemic to New Zealand.
This species was described as Aparua tuna in 1968 by Ray Forster from a single male specimen collected on Ruapuke Island. It was transferred into the Stanwellia genus in 1983. The holotype is stored at Otago Museum.
The male is recorded at 9.5mm in length. The carapace is yellow, but darker around the eyes. The legs are orange brown. The abdomen is cream with a chevron pattern dorsally.
This species is only known from Ruapuke Island, New Zealand.
Under the New Zealand Threat Classification System, this species is listed as "Naturally Uncommon" with the qualifiers of "Island Endemic" and "One Location".