Tritia unifasciata is a species of sea snail, a marine gastropod mollusk in the family Nassariidae, the Nassa mud snails or dog whelks.

The spire is composed of seven pretty distinct, but slightly convex whorls, ornamented with numerous deeply furrowed folds.

The folds of the body whorl are gradually effaced by age, and sometimes completely disappear.

These folds are crossed by very fine and very numerous transverse striae, colored with articulated, elongated, brown and whitish spots.

The general color is of a yellowish white, or fawn-color, with a brown, decurrent band above the suture, and a single other at the middle of the body whorl like a girdle.