Goniobranchus annulatus is a species of sea slug, a very colourful dorid nudibranch, a shell-less marine gastropod mollusc in the family Chromodorididae.

[2][3] Goniobranchus annulatus is a large smooth pale-bodied nudibranch with many vivid yellow spots, though these may be absent in some individuals.

The mantle usually has a purple border.

It occurs in the Red Sea, the Indian Ocean, from the East Coast of South Africa to Thailand.

[9] It is a Lessepsian migrant and has recently invaded the Mediterranean Sea, presumably through the Suez Canal.