Diloma nanum is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails.

[1][2] The small, solid, brown shell has an oval-round shape with a diameter of 5 mm.

It contains four convex, very distinct whorls.

The light-colored base of the shell is rounded and hardly perforated.

[3] This marine species occurs off the Ryukyu Islands