Viola oahuensis is a rare species of flowering plant in the violet family known by the common name Oahu violet. It is endemic to Hawaii, where it is known only from the Koolau Range on the island of Oahu. It is threatened by pigs and introduced species of plants in its habitat. It is a federally listed endangered species of the United States. This plant is a subshrub which grows up to 40 centimeters tall. It produces clusters of leaves at the ends of its branches, and whitish flowers. It grows along the upper ridges of the Koolau Mountains where the most rain falls.