Thordisa bimaculata, commonly known as the two-spotted dorid, is a species of sea slug or nudibranch in the family Discodorididae.

Both its common and scientific name refer to the two small concentrations of dark brown spots on its mantle: one behind the rhinophores and the other in front of the gills.

These patches of spots may be relatively pale or unpronounced depending on the individual, especially if covered by particles of sand or other small debris.

This species appears similar to other dorid nudibranchs in body shape: rounded overall with a squat, pointed posterior, retractable gills.

Their eggs, or nidosomes, are yellow in color, and, like other sea slugs, are laid in coiled ribbons and attached to a rocky substrate.