Nembrotha purpureolineata is a species of colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Polyceridae.

[3][4] Nembrotha purpureolineata was first described from a preserved specimen collected from Abrolhos Islands off Western Australia by O'Donoghue in 1924.

[2] The description of this species was done purely from a painting of marine life on the Great Barrier Reef in a book by William Saville-Kent, (1893)[5] and so the earlier name has been given precedence.

Although the ground colour is a creamy white, this is mostly hidden by a large brown patch which covers most of the notum.

All three species have a similar range of colour variation although N. aurea often has orange patches not present in Nembrotha purpureolineata.