Microchlamylla gracilis, sometimes known by the common name slender eolis, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Flabellinidae.

It is a fairly common species found in current-swept sites from northern France to Norway and Iceland.

It is also reported from the East coast of North America from Newfoundland south to New England.

[3] This Microchlamylla has a narrow body and cerata in well defined clusters.

The cerata have a narrow band of white pigment at the tip which is often broken into spots.