Knoutsodonta tridactila is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Onchidorididae.

[2] This species was described from Verdicio, Asturias, on the Atlantic Ocean coast of Spain, 43°35′N 005°50′W / 43.583°N 5.833°W / 43.583; -5.833.

Additional specimens were found nearby at El Puntal, 43°30′N 005°14′W / 43.500°N 5.233°W / 43.500; -5.233.

Knoutsodonta tridactila is similar in appearance to Knoutsodonta depressa but is distinguished by having a rhinophore sheath with three elongate tubercles, similar to the ones which cover the dorsal surface of the mantle.

This species was found on the bryozoan Schizomavella linearis which is a food also reported for Knoutsodonta depressa.