Austromitra lacertosa is an extinct species of sea snail, a marine gastropod mollusk in the family Costellariidae.

The shell is turriculate, ending in a relatively large pullus of two smooth convex whorls, the top laterally immersed.

The body whorl is oblong, abruptly attenuated to a short, broad, reverted beak, which is spirally ridged; flatly rounded at the suture, ornamented with acute ribs, a slightly tuberculate antesutural keel, and two approximate tubercular ridges in an alignment with posterior angle of the aperture.

The outer lip is thin, roundly insinuated at the suture and internally lirate.

[3] Fossils of this marine species were found in Miocene strata in Victoria, Australia.