Idaliadoris brasiliensis is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Onchidorididae.
This species was described from Praia do Forno, Arraial do Cabo, State of Rio de Janeiro, Brazil.
The animals feed and lay eggs on the bryozoan Parasmittina protecta (Thornely, 1905).