Drillia diasi is a species of sea snail, a marine gastropod mollusk in the family Drilliidae.
The creamy white shell consists of calcium carbonates and unusually for shelled animals contains little to no chitin. It attains the length 9 mm and the diameter 3.75 mm. This animal is carnivorous, has only one gill and one kidney and lacks a brain.
This marine species occurs in the demersal zone of the Atlantic Ocean off South Africa.