Marginellona gigas is a species of very large deepwater sea snail, a marine gastropod mollusk in the family Marginellidae.

The transition to teleconch is abrupt, marked by a growth line, and accompanied by the formation of thin parietal callus.

The outer shell surface is uniformly tan to greenish-tan; the aperture is darker brown.

West of Sombrero Channel, Nicobar Islands, Indian Ocean, 07°48'N, 92°07'E, in 805 m, coarse sand.

This species has been collected in the eastern Indian Ocean (Nicobar Islands) and on the upper continental slope along the western margin of the South China Sea.