Thorunna australis is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Chromodorididae.

[2] This species was described from New Caledonia.

It has been reported from Japan, the Philippines, Indonesia, the Marshall Islands and South Africa.

[3] This species is similar in shape and coloration to species of the Hypselodoris maculosa species complex, especially Hypselodoris paradisa.

[3]