Thorunna halourga 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 Rasch Passage, Madang, Papua New Guinea and Batangas, Philippines.

[3] The mantle is a pale lilac becoming purple in front of the rhinophores and behind the gills.

The mantle margin, which is slightly undulate, has a broad white band.

The rhinophores have a purple stalk and the lamellae are edged with orange.