Acanthodoris brunnea, common name the brown horned dorid, is a species of sea slugs, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Onchidorididae.

It has been reported from Vancouver Island, British Columbia south to Santa Monica Bay.

[4][5] Specimens from Monterey Bay have been sequenced for the 16S ribosomal RNA and CO1 genes.

[6][7] A. brunnea has a brown mantle with white and black spots.

It is described that when handled, Acanthodoris brunnea emit the smell of cedar.