[1][2] It is part of the C. trilobus aggregate, whose members are characterized by a funnel or dish-shaped labellum and an often heart or kidney-shaped solitary leaf.

[2] Corybas sanctigeorgianus is a terrestrial, perennial herb with a solitary reniform (kidney-shaped) to cordiform (heart-shaped) leaf born on a petiole that is 9.8–12.7 mm long.

The dorsal sepal is green, sometimes splotched with maroon, and arches over the labellum and is broadly rounded at the apex, although sometimes it is mucronate.

The lip is strongly downturned; it folds inwards and forms a central groove, and its sides are slightly cupped.

[4][2] Corybas sanctigeorgianus is endemic to the Hunua Ranges of New Zealand's North Island and grows in leaf litter under scrub or podocarp-broadleaved forest, gravelly soil, or the decaying trunks of tree ferns.