Cassis cornuta, common name the horned helmet, is a species of extremely large sea snail, a marine gastropod mollusc in the family Cassidae, the helmet shells and their allies.

It has a very solid, heavy, rotund shell with large, horn-like knobs and a wide, flat base.

[1] This large sea snail is found on sand and coral rubble, often around reefs.

In some places the snail is hunted for meat and is traditionally roasted in the shell over fire.

Because this snail hunts the crown-of-thorns starfish, which feed on corals, Cassis cornuta has been put under strict protection in Queensland.