Clavatula diadema common name the diadem turrid, is a species of sea snail, a marine gastropod mollusk in the family Clavatulidae.
The size of an adult shell varies between 14 mm and 38 mm. Shells typically have the opening on the right side. The shape of top of the shell is a steep cone with small rigid protrusions circling each layer.
This species occurs in the Atlantic Ocean from Senegal to Angola.