The three-spot nudibranch, scientific name Aldisa trimaculata, is a species of sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Cadlinidae.
The three-spot nudibranch is a tan-coloured dorid with a warty skin and three brown spots, which are themselves spotted with lighter patches. The animal has eight gills arranged around the anus and its rhinophores are perfoliate. It may reach a total length of 40 mm.
This demersal species has so far only been found around the southern African coast, on both sides of the Cape Peninsula, in 10–30 m of water. It may possibly be endemic to that area.
This species feeds on sponges.