Tectus royanus is a species of sea snail, a marine gastropod mollusk in the family Tegulidae.

In adult shells the upper surface is invariably covered with algae, coralline and other, while the base usually supports a colony of Serpula.

The shell is covered with very low rounded nodules along the lower edge, there being about 15 at a distance of 2 cm.

The whole exterior is ornamented by close spiral beaded ribs, about 10 to a centimetre, crossed by diagonal growth lines, and covered with a white calcareous coating.

But near the interior, where the coating is absent, it shows regular spiral threads, which are closest along the exterior margin.