Powellisetia unicarinata is a species of marine gastropod mollusc in the family Rissoidae.

[1] First described by Powell in 1930 as Notosetia unicarinata, it is endemic to the waters of New Zealand.

[3] Powellisetia bilirata has a minute, roughly ovate shell with a single strong spiral ridge.

[3] The species is similar in appearance to Powellisetia porcellanoides, but can be distinguished by its angled carnate shoulder.

[1] The holotype dredged by Powell in 1924, from a depth of 9–11 metres at Tryphena Bay on Great Barrier Island.