Aplysiopsis sinusmensalis, the Table Bay nudibranch, is a species of sacoglossan sea slug, a shell-less marine opisthobranch gastropod mollusk in the family Hermaeidae.

[2][3] It has been found off Blouberg, Milnerton, Oudekraal and Llandudno on the Atlantic coast of the Cape Peninsula and at Buffels Bay in False Bay.

[4] The Table Bay nudibranch is small, growing up to 20mm in total length.

It has a lighter brown white-margined band extending down the back of the head.

[5] The Table Bay nudibranch has been found in shallow water, mainly estuaries and tidal pools, on the green algae Ulva sp.