Subvestinautilus is a genus of evolute koninckioceratids, in the order Nautilida, with a depressed, trapezoidal whorl section.

The venter is broadly rounded, ventrolateral shoulders sharply rounded, flanks flattened and converging toward a narrow rounded dorsum.

In early growth stages a keel forms on the umbilical shoulder which becomes rounded or marked by a longitudinal rib at maturity .

Subvestinautilus, named by Turner, 1954, has been found in the Lower Carboniferous of Ireland and the Isle of Man.

This prehistoric nautiloid-related article is a stub.