[3][1] It has a solitary heart-shaped leaf and a deep crimson or nearly black flower and is part of the Corybas trilobus aggregate.

[4] Corybas obscurus is a terrestrial, perennial herb with a single reniform (kidney-shaped) or cordiform (heart-shaped) leaf born on a petiole that is 5.1–40.8 mm long.

It is curved at its base, forming a cylindrical opening with a flared, highly fimbriate (toothed) mouth.

However, C. obscurus has a short dorsal sepal firmly pressed against the upper border of the labellum and a reniform to cordiform leaf.

Its specific epithet is a Latin word that means "hidden" or "concealed" and refers to the dark color of the flower.