Haustrum haustorium, common name: the brown or dark rock shell, is a large species of predatory sea snail, a marine gastropod mollusc in the family Muricidae, the murex snails or rock snails.

However, Beu (2004) reclassified a number of New Zealand's whelks, considering species in the genus Lepsiella to be synonymous with the genus Haustrum.

A reliable characteristic for distinguishing Haustum haustorium from its congeners is the angle by which the aperture lip inserts on the shell: In Haustrum haustorium the angle is near-perpendicular, whereas in other species the angle is more acute (~45 degrees).

This rock snail's typical habitat is the mid and lower eulittoral zone of New Zealand's semi-exposed rocky intertidal shores.

It is less common on algal-dominated sheltered shores.