Rubus mortensenii is a species of flowering plant in the family Rosaceae.
Rubus mortensenii has sharply angular reddish turions with thorns from 2–4 mm long. The limb has regular rounded teeth. The final leaflet has a clearly distinct apex, long and thin, around 15 mm. Its upper face has between 5-100 hairs per cm2. Its lower face meanwhile, is greyish-green to gray in color. The bright pink flowers are eight to ten millimeters long.
It is native to Sweden, Denmark and Germany. The species is common, occurring on non-calcareous soil, in thickets, clearings, and the edges of wood.