Genoplesium trifidum is a terrestrial, perennial, deciduous, herb with an underground tuber and a single thin leaf 200–300 mm (8–10 in) long and fused to the flowering stem with the free part 15–20 mm (0.6–0.8 in) long.

There is a broad, tapering callus in the centre of the labellum and extending nearly to its tip.

[2][3][4] The blackish midge orchid was first formally described in 1941 by Herman Rupp who gave it the name Prasophyllum trifidum and published the description in The Victorian Naturalist.

[5][6] In 2022, Matthew Renner changed the name to Genoplesium trifidum[3][7] and the name is accepted by Plants of the World Online.

[1] The specific epithet (trifidum) is a Latin word meaning "three-cleft",[8] referring to the shape of the column.