Okenia purpureolineata is a species of sea slug, specifically a dorid nudibranch, a marine gastropod mollusc in the family Goniodorididae.
This species was described from Okinawa, Ryukyu Islands, Japan.[1]
This Okenia has a narrow body and seven pairs of long lateral papillae. There are two papillae on the mid-line of the back, in front of the gills. The body is translucent purple and there is a network of dark purple lines on the back running from in front of the rhinophores to behind the gills.
The diet of this species is the ctenostome bryozoan, Amathia sp.