Umbonium sagittatum is a species of very small sea snail, a marine gastropod mollusc or micromollusc in the family Trochidae, the top snails.

The shell is smaller and more depressed than is the case in Umbonium vestiarium.

The basal callus is convex, circular, and smaller than in Umbonium vestiarium and it is either white or slate-colored.

The surface of the shell is perfectly smooth and polished.

[1] This marine species occurs in the Makassar Strait.