Dendronotus frondosus, sometimes known by the common name frond eolis or bushy backed nudibranch, is a species of sea slug, specifically a dendronotid nudibranch, a marine gastropod mollusc in the family Dendronotidae.

A specimen from Norway has been designated as a neotype.

[4] This species has been reported from the north-east and north-west Atlantic Ocean.

[5] Records from the Pacific Ocean are now known to be distinct species.

[4] The size of the body attains 100 mm.