• Trochus is a genus of medium-sized to large, top-shaped sea snails with an operculum and a pearly inside to their shells, marine gastropod molluscs in the family Trochidae, the top snails.

• When the word "trochus" or "Trochus" is used in reference to fishing sea snails for commercial purposes, the usual species targeted is Tectus niloticus, which is valued for its nacre or mother of pearl layer, which was traditionally made into items such as pearl buttons and jewellery.

• Tectus niloticus is no longer classified as a Trochus species, and it is no longer classified in the family Trochidae; it is now placed in the family Tragulidae.