Doto onusta is a species of sea slug, a nudibranch, a marine gastropod mollusc in the family Dotidae.

Henning Lemche identified it with the common species which feeds on the hydroid Dynamena pumila, predominantly in the intertidal region.

[3] This nudibranch is translucent white with dark red spots on the ceratal tubercles.

The back and sides are spattered with red pigment which extends up the inner faces of the rhinophore sheaths.

[5] Doto onusta feeds on the hydroid Dynamena pumila, family Sertulariidae.