It has a single thick, broad, leathery leaf and up to twenty five relatively large dark blue to purplish flowers with white, toothbrush-like tufts.Thelymitra macrophylla is a tuberous herbaceous perennial with a single thick, leathery, strap-like leaf 150–500 mm (6–20 in) long and 5–25 mm (0.2–1 in) wide.

The flowers are strongly scented, insect pollinated and open in sunny weather.

[1][2][3] Thelymitra macrophylla was first formally described in 1840 by John Lindley from a specimen collected by James Drummond and the description was published in A Sketch of the Vegetation of the Swan River Colony.

[5]: 466 The large-leafed sun orchid is widespread and common between Perth and Albany, growing in jarrah forest and wandoo woodland.

[6] Thelymitra macrophylla is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.