Diloma zelandicum is a species of sea snail, a marine gastropod mollusc in the family Trochidae, the top snails or top shells.

The imperforate shell is depressed and has an orbiculate-conoidal shape.

They are spirally sulcate, the sulci about 5 on the penultimate whorl.

The body whorl is much dilated, slightly depressed above, rounded in the middle, very obliquely striate, obsoletely transversely sulcate, slightly convex beneath.

The columellar callus is broadly expanded, subdepressed at the place of the umbilicus.