The purple sunstar, northern sunstar, or smooth sun star, Solaster endeca, is a species of starfish in the family Solasteridae.

Description Solaster endeca normally grow to an adult size of about 20 centimetres (7.9 inches) but in some cases reach 40 cm (16 in). It is a robust species with 9 or 10 arms (occasionally any number from seven to 13) set around a large disc. The aboral (upper) surface is formed of calcareous plates densely covered with paxillae, peg-like projections covered in tiny spinelets. No pedicellariae are present, but groups of two to three gills are found between the plates. On the oral (under) surface, the row of plates on either side of the ambulacral groove bear two or three spines and several rows of shorter spines, with two rows of tube feet. S. endeca ranges in colour from greyish-cream to pinkish-purple. The arms are often turned up at the tips, showing the pale oral surface. It can be confused with Crossaster papposus , the only British species with a similar number of arms, but S. endeca has a smoother aboral surface.

The purple sun star occurs in the northeastern Atlantic Ocean and the North Sea at depths to 450 m (1,480 ft).